Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1998-05-29
2001-01-16
Nguyen, Hoa T. (Department: 2753)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S077020
Reexamination Certificate
active
06175465
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a head positioning control system applicable to a disk storage drive such as a hard disk drive (HDD) or the like, and particularly, to a head positioning control system (or servo-system) using a MR (magnetoresistive) head as a read head.
Conventionally, in a disk storage drive such as a HDD or the like, a magnetic head is used to write data on a disk as a storage medium and to read data from a disk. Other than a magnetic disk drive such as a HDD, a magneto-optical disk may be considered as a disk drive. As a practical example of the present invention, a HDD is cited in the following explanation.
In recent years, in order to realize a higher recording density, a head of a read/write separation type using a MR (magnetoresistive) head as a read head has been put to use. This type of head has a structure in which a read head (MR head) and a write head (inductive head) are equipped on a slider as a main body of the head.
In a HDD, when making access with specified data in a disk (to read or write data), operation for reading servo data previously recorded on a disk is read by a read head. A CPU of the HDD uses the servo data read by the read head, to make positioning control by which the position of the read head on the disk is detected and the read head is moved to a target position to be accessed. The target position to be accessed means a track (or cylinder) specified for reading or writing data. In writing operation, the write head is positioned at a specified track, by the positioning control of the read head.
Head positioning control made by the CPU can be roughly divided into seek control (or speed control) for moving a head to a target track and track following control (or fine position control) for positioning the head to a certain range of the target track. The seek control uses a track address (or cylinder code) contained in servo data. Meanwhile, the position control (or track following control) uses servo burst data (a, b, c, and d) described later. The present invention relates to position control using servo burst data.
In the following, position control in a servo system (or head positioning control system) of a HDD will be briefly explained with reference to
FIGS. 8 and 9
.
As shown in
FIG. 8
, a number of coaxial tracks (N−1, N, N+1, are provided in a disk
1
. In
FIG. 8
, the range from a position X
1
to a position X
5
corresponds to the range of a track N. A servo area is provided at a same position in the radial direction in each of the tracks. Servo areas are arranged with an equal intervals inserted between each other in the circumferential direction of the disk
1
. Servo data including a cylinder code described above and servo burst data is previously recorded in the servo area (by a specialized servo writer when manufacturing a HDD).
FIG. 8
shows only servo burst data (a, b, c, and d). In the following, burst patterns of items of the servo data are expressed as small letters a to d, and amplitude values (of digital values which will be explained later) reproduced from the burst pattern items are expressed as burst data items A to D. In each of the tracks, a data sector (which is an area for recording user data) is provided between the servo areas.
Servo burst data consists of burst patterns a and b arranged at right angles to the track center (which is the center X
3
of the track N) as a reference, and burst patterns c and d arranged at right angles to a boundary position (X
5
or X
1
) as a reference.
The servo system (CPU) makes seek control to move a read head
3
to the vicinity of a specified track (N), and then, sample-holds amplitude values corresponding to burst patterns a to d read out by the read head
3
. The CPU inputs position data items A to D obtained by converting the amplitude values into digital values. Further, the CPU executes calculation processing (or positional displacement calculation) for detecting the position (or positional displacement from a reference position) of the read head
3
with use of the burst data items A to D obtained.
Specifically, when the read head
3
is positioned in the vicinity of the center (X
3
) of the track N, as shown in
FIG. 8
, the CPU inputs position data items A and B corresponding to burst pattern items a and b, and executes calculation of “PI=(A−B)/(A+B)”. Position information PI calculated by the calculation is equivalent to a positional displacement amount E of the read head
3
from the center position X
3
of the track N as a reference. The CPU executes position controls of the read head
3
so that the position displacement amount E is eliminated to zero.
Meanwhile, as shown in
FIG. 8
, as a HDD has come to have a higher recording density, the head width of the read head
3
has been decreased. Therefore, the relationship between the head width TW and a track pitch (or track width) satisfies “TP>TW”. This track width TP is a track range for positioning the read head
3
. When the head width TW and the track width TP thus satisfy the relationship of “TP>TW”, the read head
3
is out of the range of the burst pattern b if the read head is in the vicinity of the position X
5
, and therefore, the burst data B is always zero. Therefore, the CPU cannot obtain proper position information PI from the calculation “PI=(A−B)/(A+B)”. As for the CPU the vicinity of the position X
5
in the track range is an insensible band in detection of the position of the read head
3
. Therefore, the CPU executes calculation of “PI=(C−D)/(C+D)”, using burst data items C and D corresponding to burst patterns c and d, to calculate a positional displacement amount E of the read head
3
from the track boundary position X
5
(as shown in FIGS.
9
and
10
). In
FIGS. 9 and 10
, the lateral axis denotes a head position (HP
9
) and the longitudinal axis denotes position information (or a position displacement) PI. Also, the continuous line
100
indicates position information based on a result of the calculation “PI=(A−B)/(A+B)” and the broken line
101
indicates position information based on a result of the calculation “PI=(C−D)/(C+D)”. In
FIG. 10
, the broken line
101
indicates position information including a shift amount (+1) equivalent to half of one track.
As has been described above, since the relationship between the head width TW and the track width TP satisfies “TP>TW”, the calculated position information PI is greater than the actual shift amount (E) of the read head
3
, and this was confirmed from experiments. Hence, the CPU sets a position-conversion factor K and makes a correction by multiplying the position information by the factor K. Note that the position-conversion factor K is a fixed value set by TP and TW.
PI={
(
A−B
)/(
A+B
)}
*K
(1)
In correction of position information with respect to the position X
5
as a reference, position information PI is naturally obtained by multiplying a result of “(C−D)/(C+D)” by the factor K. By improving the position conversion factor K, the CPU is capable of obtaining position information PI having a so-called linearity. In
FIG. 11
, the continuous line
111
indicates a calculation result of the calculation formula (1), and the broken line
112
indicates position information obtained by taking into consideration a shift amount (+0.5 track) of a half track.
As described above, in a servo system of a HDD, the CPU executes calculation processing related to position information for detecting a position of a read head (or position displacement amount from a reference position), with use servo burst data. In the calculation processing, the CPU uses a predetermined position factor K to calculate position information having a linearity. As a result of this, the CPU is capable of detecting accurately the position of a head from position information having a linearity, and of controlling positioning of a head with respect to a target
Kawachi Hidetoshi
Kusumoto Tatsuharu
Yatsu Masahide
Davidson Dan I.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Nguyen Hoa T.
LandOfFree
Head positioning control system for use in a disk storage drive does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Head positioning control system for use in a disk storage drive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Head positioning control system for use in a disk storage drive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2493067