Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1998-05-06
2001-07-24
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S077020, C360S077080, C360S078050
Reexamination Certificate
active
06266205
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to magnetic disk drive storage systems and, more specifically, to a method and an apparatus for combining servo sector positioning information with other non-servo sector positioning information to more accurately position a transducer over tracks on a disk of a disk drive system which utilizes an embedded servo sector scheme.
BACKGROUND OF THE INVENTION
A magnetic disk drive system is a digital data storage device that stores digital information within concentric tracks on a storage disk (or platter). The storage disk is coated with a magnetic material that is capable of changing its magnetic orientation in response to an applied magnetic field. During operation of a disk drive, the disk is rotated about a central axis at a substantially constant rate. To write data to or read data from the disk, a magnetic transducer is positioned above a desired track of the disk while the disk is spinning. As is well-known in the art, different techniques may be used to move the transducer from a current track to the desired track so that the transducer is properly positioned over the desired track for reading and writing.
Writing is performed by delivering a write signal having a variable current to a transducer while the transducer is held close to the rotating disk over the desired track. The write signal creates a variable magnetic field at a gap portion of the transducer that induces magnetic polarity transitions into the desired track. The magnetic polarity transitions are representative of the data being stored.
Reading is performed by sensing magnetic polarity transitions previously written on tracks of the rotating disk with the transducer. As the disk spins below the transducer, the magnetic polarity transitions on the track present a varying magnetic field to the transducer. The transducer converts the magnetic signal into an analog read signal that is then delivered to a read channel for appropriate processing. The read channel converts the analog read signal into a properly timed digital signal that can be recognized by a host computer system external to the drive.
The transducer is often dual-purpose, meaning the same transducer can both read from and write to the magnetic disk. Combining read and write functions into the same transducer allows some of the structure used for writing also to be used for reading. A dual purpose transducer cannot perform both read and write functions at the same time because, among other reasons: (1) their shared structures generally prohibit use of both functions at one time; and, (2) the magnetic field generated during a write operation tends to saturate the sensitivity of the read element.
Portions of a standard disk drive, generally designated
1
, are illustrated in FIG.
1
. The disk drive comprises a disk
4
that is rotated by a spin motor (not shown). The spin motor is mounted to a base plate (not shown). Data is stored on magnetic material which coats the two surfaces
5
(only one surface
5
is shown in
FIG. 1
) of the disk
4
. An actuator arm assembly
7
is also mounted to the base plate.
The actuator arm assembly
7
includes a transducer
10
mounted to a microactuator arm
13
which is attached to an actuator arm
16
. The actuator arm
16
rotates about a bearing assembly
19
. The actuator arm assembly
7
cooperates with a voice-coil motor (VCM)
22
which moves the transducer
10
relative to the disk
4
. The spin motor, voice-coil motor
22
and transducer
10
are coupled to a number of electronic circuits mounted to a printed circuit board (not shown). The electronic circuits typically include a read channel chip, a microprocessor-based controller and a random access memory (RAM) device, among other things.
The standard disk drive of
FIG. 1
has a plurality of disks as shown in FIG.
2
. Each of the plurality of disks
4
has two surface
5
, with magnetic material on each of those surface
5
. Therefore, in the disk drive shown in
FIG. 2
, two actuator arm assemblies
7
are provided for each disk
4
. Each actuator arm assembly
7
has a transducer
10
which converts between electrical energy and magnetic energy. To position the transducer
10
, the VCM
22
moves all actuator arms
16
in unison relative to their respective disks
4
. It should be noted that generally only one transducer
10
is active at a time.
All actuator arms
16
in a multiple disk storage device are ganged together so that they move in unison with respect to the disk
4
. The actuator arms
16
perform coarse positioning of the transducer
10
, while the microactuator arms
13
perform fine position adjustments so that the transducer
10
is centered over a track
25
(see FIG.
1
). As shown in
FIG. 1
, each microactuator arm
13
is pivotally connected to its respective actuator arm
16
and is capable of pivotable movement independent from the actuator arm
16
, which allows for fine position adjustments. Movement of each microactuator arm
13
can be independently optimized for imperfections in the arcuate geometry of each track
25
on its corresponding magnetic surface
5
. Although
FIGS. 1 and 2
depict a transducer positioning system which contains both actuators and microactuators, more commonly, the combination of both positioning methods are not used in a given hard drive
1
.
Actuator arm assemblies
7
containing both microactuator arms
13
and actuator arms
16
are, in some ways, advantageous as compared to actuator arm assemblies
7
containing solely actuator arms. For example, microactuator arms
13
have a smaller mass and are shorter in length, which allows them to be moved more rapidly onto the track centerline
40
(see
FIG. 3
) as compared to actuator arms
16
.
Referring to
FIGS. 1 and 3
, data is stored on the disk
4
within a number of concentric radial tracks
25
(or cylinders). Each track
25
is divided into a plurality of sectors, and each sector is further divided into a servo region (or servo sector)
28
and a data region
31
.
Servo sectors
28
are used to, among other things, provide transducer position information so that the transducer
10
can be accurately positioned by the actuator arm
16
and/or microactuator arm
13
over the track
25
, such that user data can be properly written onto and read from the disk
4
. The data regions
31
are where non-servo related data (i.e., user data) is stored and retrieved. Such data, upon proper conditions, may be overwritten. Because servo sectors
28
are embedded into each track
25
on each disk
4
between adjacent data regions
31
, this type of servo-scheme is known by those skilled in the art as an embedded servo scheme.
As understood by those skilled in the art, it is desirable write information to and read information from a fixed position relative to the centerline
40
of the track
25
. For ease of discussion, it is presumed within this application that the information is written to the track centerline
40
, but the invention should not be so limited. After writing to the track centerline
40
, the track centerline would contain a stronger magnetic signal than other portions of the track away from the centerline. The portion of the track
25
storing the strongest magnetic signal is defined herein as the magnetic center of the track. For the purposes of this application it is presumed information is written to the track centerline
40
which would mean the magnetic center of the track corresponds with the track centerline.
FIG. 3
shows a portion of a track
25
of a disk
4
drawn in a straight, rather than arcuate, fashion for ease of depiction. As is well-known, tracks
25
on magnetic disks
4
(as depicted in
FIG. 1
) are circular. Referring again to
FIG. 3
, each track
25
has a centerline
40
. To accurately write data to and read data from the data region
31
of the track
25
, it is desirable to maintain the transducer
10
(see
FIG. 1
) in a relatively fixed position with respect to a given track's centerline
40
during each of the writing and reading procedures.
Guo Lin
Schreck Erhard T.
Davidson Dan I.
Hudspeth David
Maxtor Corporation
Sigmond David M.
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