US-20260128060-A1 - DATA STORAGE DEVICE WITH ASSISTIVE BURSTS IN SERVO SECTORS

US20260128060A1US 20260128060 A1US20260128060 A1US 20260128060A1US-20260128060-A1

Abstract

Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: during a read operation, open a servo gate in the selected head in order to read the first servo bursts, the sync mark, and the second servo bursts in one of the servo sectors; and determine a position error signal for the selected head based on reading the first servo bursts and the second servo bursts.

Inventors

Guoxiao Guo
Charles A. Park
YUN HONG
Scott A. Ottele
Gary Herbst
Satoshi Yamamoto

Assignees

WESTERN DIGITAL TECHNOLOGIES, INC.

Dates

Publication Date: 20260507
Application Date: 20241105

Claims (20)

1 . A data storage device, comprising: one or more disks each comprising a plurality of servo sectors defining a plurality of data tracks, wherein each of the servo sectors comprises first servo bursts followed by a sync mark followed by second servo bursts; an actuator mechanism configured to position a selected head among one or more heads proximate to a corresponding disk surface of a corresponding disk among the one or more disks; and one or more processing devices, individually or in combination, configured to: during a read operation, open a servo gate in the selected head to read the first servo bursts, the sync mark, and the second servo bursts in one of the servo sectors; and determine a position error signal for the selected head based on reading the first servo bursts and the second servo bursts.
2 . The data storage device of claim 1 , wherein the read operation is configured to read data stored in a data sector immediately following the one of the servo sectors.
3 . The data storage device of claim 1 , wherein each of the servo sectors further comprises a track identifier (ID) between the first servo bursts and the second servo bursts.
4 . The data storage device of claim 1 , wherein each of the servo sectors is devoid of a preamble.
5 . The data storage device of claim 1 , wherein each of the servo sectors further comprises a preamble between the first servo bursts and the second servo bursts.
6 . The data storage device of claim 1 , wherein the position error signal comprises an average of a first position error signal determined using the first servo bursts and a second position error signal determined using the second servo bursts.
7 . The data storage device of claim 6 , wherein the average is a weighted average based on a first number of burst cycles associated with reading the first servo bursts and a second number of burst cycles associated with reading the second servo bursts.
8 . The data storage device of claim 1 , wherein: the first servo bursts comprise a first burst and a second burst; the second servo bursts comprise a third burst and a fourth burst; the first burst and the third burst are a first burst type; and the second burst and the fourth burst are a second burst type different than the first burst type.
9 . The data storage device of claim 8 , wherein the position error signal is determined using a sum of values obtained by reading the first burst and the third burst and a sum of values obtained by reading the second burst and the fourth burst.
10 . The data storage device of claim 8 , wherein the determining the position error signal comprises: performing a first asynchronous position error signal calculation using the first burst and the second burst; performing a second asynchronous position error signal calculation using the third burst and the fourth burst; and determining the position error signal based on the first asynchronous position error signal calculation and the second asynchronous position error signal calculation.
11 . The data storage device of claim 1 , wherein each of the servo sectors further comprises repeatable runout (RRO) correction data.
12 . The data storage device of claim 11 , wherein the RRO correction data is followed by the sync mark.
13 . The data storage device of claim 1 , wherein the one or more processing devices, individually or in combination, are further configured to control a position of the selected head using the position error signal.
14 . The data storage device of claim 1 , wherein: the first servo bursts comprise a first split burst servo pattern; and the second servo bursts comprise a second split burst servo pattern.
15 . A method comprising: during a read operation, opening a servo gate in a selected head in order to read first servo bursts followed by second servo bursts in a servo sector that is devoid of a preamble and devoid of a sync mark; determining a position error signal for the selected head based on reading the first servo bursts and the second servo bursts; and controlling a position of the selected head using the position error signal, wherein the opening the servo gate, the determining the position error signal, and the controlling the position of the selected head are performed by one or more processing devices individually or in combination.
16 . The method of claim 15 , wherein: the first servo bursts comprise a first burst and a second burst; the second servo bursts comprise a third burst and a fourth burst; the first burst and the third burst are a first burst type; and the second burst and the fourth burst are a second burst type different than the first burst type.
17 . One or more processing devices comprising, individually or in combination: means for opening a servo gate in a selected head, during a read operation, to read repeatable runout (RRO) correction data followed by a sync mark followed by servo bursts in a servo sector; means for generating a control signal for the selected head based on reading the RRO correction data and the servo bursts; and means for controlling a position of the selected head using the control signal.
18 . The one or more processing devices of claim 17 , wherein: the servo sector comprises first servo bursts preceding the sync mark; the servo bursts following the sync mark comprise second servo bursts; and the control signal is generated based on reading the RRO correction data, the first servo bursts, and the second servo bursts.
19 . The one or more processing devices of claim 18 , further comprising, individually or in combination, means for determining a position error signal using respective values obtained by reading the first servo bursts and the second servo bursts.
20 . The one or more processing devices of claim 17 , wherein the servo sector comprises a preamble between the RRO correction data and the sync mark.

Description

BACKGROUND Data storage devices such as disk drives comprise a disk and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk. The disk comprises a plurality of radially spaced, concentric tracks for recording user data sectors and servo wedges or servo sectors. The servo sectors comprise head positioning information (e.g., a track address) which is read by the head and processed by a servo control system to control the actuator arm as it seeks from track to track. FIG. 1 shows a prior art disk format 2 as comprising a number of radially-spaced, concentric servo tracks 4 defined by servo wedges 60-6N recorded around the circumference of each servo track. A plurality of concentric data tracks are defined relative to the servo tracks 4, wherein the data tracks may have the same or a different radial density (e.g., tracks per inch (TPI)) than the servo tracks 4. Each servo wedge 6i comprises a preamble 8 for storing a periodic pattern, which allows proper gain adjustment and timing synchronization of the read signal, and a sync mark 10 for storing a special pattern used to symbol synchronize to a servo data field 12. The servo data field 12 stores coarse head positioning information, such as a servo track address, used to position the head over a target data track during a seek operation. Each servo wedge (e.g., servo wedge 64) further comprises groups of phase-based servo bursts 14 (e.g., N and Q servo bursts), which are recorded with a predetermined phase relative to one another and relative to the servo track centerlines. The coarse head position information is processed to position a head over a target data track during a seek operation, and the servo bursts 14 provide fine head position information used for centerline tracking while accessing a data track during write/read operations. A position error signal (PES) is generated by reading the servo bursts 14, wherein the PES represents a measured position of the head relative to a centerline of a target servo track. A servo controller processes the PES to generate a control signal applied to one or more head actuators in order to actuate the head radially over the disk in a direction that reduces the PES. The one or more head actuators may comprise a voice coil motor, as well as one or more fine control actuators such as milliactuators or microactuators, in some examples. SUMMARY Various examples disclosed herein provide data storage devices such as hard disk drives with control circuitry configured to perform novel and inventive position error signal determination using values obtained by reading respective first servo bursts and second servo bursts in a servo sector that is devoid of a preamble. In various examples, the servo sector includes the first servo bursts followed by a sync mark followed by the second servo bursts in a longitudinal direction of a track containing the servo sector. In some embodiments, since the servo sector does not include a preamble, the first servo bursts may be written at the beginning region of the servo sector where the preamble normally would be written. In embodiments, the first servo bursts written in this region of the servo sector provide the servo sector with additional servo bursts compared to servo sectors that include a preamble at this region. In embodiments, the additional servo bursts increase the amount of servo burst information that is usable in determining the PES, which advantageously reduces the repeatable runout (RRO) component of the PES associated with read operations. Various illustrative aspects are directed to a data storage device comprising: one or more disks each comprising a plurality of servo sectors defining a plurality of data tracks, wherein each of the servo sectors comprises first servo bursts followed by a sync mark followed by second servo bursts; an actuator mechanism configured to position a selected head among one or more heads proximate to a corresponding disk surface of a corresponding disk among the one or more disks; and one or more processing devices. The one or more processing devices, individually or in combination, are configured to: during a read operation, open a servo gate in the selected head in order to read the first servo bursts, the sync mark, and the second servo bursts in one of the servo sectors; and determine a position error signal for the selected head based on reading the first servo bursts and the second servo bursts. Various illustrative aspects are directed to a method comprising: during a read operation, open a servo gate in a selected head in order to read first servo bursts followed by second servo bursts in a servo sector that is devoid of a preamble; determine a position error signal for the selected head based on reading the first servo bursts and the second servo bursts; and control a position of the selected head using the position error signal, wherei