Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1998-07-22
2002-11-05
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S077050, C360S053000
Reexamination Certificate
active
06476997
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk device, a track positioning method, and a method for generating a position error signal which are used in a hard disk drive (HDD) or the like, and particularly to a disk device, a track positioning method, and a method for generating a position error signal in which a magnetic head is positioned at the center of a target track.
2. Description of Related Art
In the hard disk drive (HDD) which is used as an external storage device for information processing systems, more size reduction and higher reliability are demanded. In the conventional hard disk, data tracks are concentrically formed. A reading or writing of information to the magnetic disk is performed after a seek operation, that is, after rotating the magnetic disk and moving the magnetic head substantially radially of the magnetic disk to position the magnetic head at a specific data track. The positioning of the magnetic head at a specific data track is performed by using the magnetic head to respectively read head position identifying information and burst patterns which are prerecorded on the magnetic disk.
FIG. 7
is a figure schematically showing the data areas and the servo areas of a magnetic disk. As shown in
FIG. 7
, data areas
11
and servo areas
12
are separately formed in a magnetic disk
10
, and a magnetic head identifies the position according to the servo data recorded in these servo areas
12
, and writes data to the data area at a desired position, or reads it.
FIG. 8
is a figure showing part of the head position identifying information and burst patterns which are recorded on the magnetic disk. In
FIG. 8
, the magnetic disk rotates along the circumferential direction (the direction of arrow F in FIG.
8
), and the magnetic head, not shown, moves along substantially the radial direction of the magnetic disk (the direction of arrow G in FIG.
8
). Concentrically formed in the magnetic disk are a plurality of data tracks
20
A,
20
B,
20
C, . . . on which data are recorded. Data tracks are arranged along the circumferential direction, and between the adjacent data tracks, an identifying information recording area
21
and a burst pattern recording area
22
are formed.
The cylinder (CYL) and sector (SEC) position information, which is information for identifying the head position, is contained in the gray code (cyclic binary code) in the identifying information recording area
21
. Following the gray code, the burst pattern recording area
22
for providing a fine adjustment signal for the track at the head position is recorded on the disk. By reading these servo data, the magnetic head is positioned at a desired track.
Each data track is previously provided with a track address for identifying itself. Recorded in the identifying information recording area
21
is identifying information of a predetermined number of bits which is representing the track address of the corresponding data track by a gray code. Also recorded in the burst pattern recording area
22
is a plurality of (in
FIG. 8
, four) burst pattern rows
22
A,
22
B,
22
C, and
22
D in which regions having a signal recorded therein (refer to the hatching in
FIG. 8
) are respectively arranged along the radial direction of the disk.
When the magnetic head is positioned at a desired data track, the track address of a data track which the magnetic head is facing is calculated according to an identifying information read signal, which is outputted from the magnetic head each time the head crosses the identifying information recording area
21
.
FIGS.
9
(A)-(C) illustrate the use of the gray code in the magnetic disk. FIG.
9
(A) illustrates the identifying information, wherein the record length for one-bit data (L in FIG.
9
(A)) is predetermined. According to whether the value of each bit of the gray code representing a track address is “0” or “1,” the recording is made so as to make different the positions of the portions to be magnetized to N or S in a recording region of the length L which is corresponding to each bit.
For instance, if the magnetic head passes the identifying information recording area of a data track N shown in FIG.
9
(A), a pulse is generated at a portion magnetized to N or S as shown in FIG.
9
(B). Further, if the magnetic head passes the identifying information recording area of a data track N+1 shown in FIG.
9
(A), a pulse is generated at a portion magnetized to N or S as shown in FIG.
9
(C).
Based on the positions of the pulses of these identifying information read signals, the value of the gray code recorded in the identifying information recording area can be determined, and a track address can be obtained by converting the determined gray code to a binary code. For instance, a gray code (100) is determined from the pulse train of FIG.
9
(B), and a binary code (111) is obtained through the conversion of the gray code. Further, a gray code (000) is determined from the pulse train of FIG.
9
(C), and a binary code (000) is obtained through a further conversion of this gray code.
If it is determined that the magnetic head has reached the target data track, a position detection signal the level of which linearly varies according to the magnetic head position is generated by analyzing the sum of a plurality of signals obtained by respectively reading the plurality of burst pattern rows in the burst pattern recording area
22
. Based on the position detection signal, the magnetic disk is positioned so that the gap of the magnetic head is positioned at the center of the width of the target data track.
As described above, in the sector servo type magnetic disk device, a seek operation is performed for moving the magnetic head onto a target track on the magnetic disk. In the seek operation, there is a speed control in which the servo data prerecorded on the magnetic disk is read out by the magnetic head and the magnetic head is moved to the target track on the magnetic disk according to the servo data that has been read out. There is a further speed control in which, when the magnetic head approaches the target track, the magnetic head is moved to the target track based on the burst pattern read out by the magnetic head. Further, there is a tracking control for positioning the magnetic head at the center of the target track. In addition, also in the tracking control, by moving the magnetic head according to the burst pattern detected by the magnetic head from the target track on the magnetic disk, the magnetic head is positioned at the center of the target track on the magnetic disk. That is, a tracking control is performed in which, if an off-track occurs in the magnetic head, the displacement is corrected to provide on-track control.
However, in the above magnetic disk device, if the magnetic layer formed on the magnetic disk surface peels off or dust is deposited when the magnetic layer is formed, the particular portion easily develops a defect as data is recorded with a high density. If such defect occurs in the recording area of a burst pattern, which is position information for obtaining the positional displacement of the magnetic head from the center of a track, the burst pattern is not correctly read by the magnetic head. As a result, the magnetic head may be determined to be off the center of the target track, when in fact the magnetic head is on the center of the track.
In the above HDD (Hard Disk Drive) using sector servo, if there is a defect in a burst pattern for creating a PES (Position Error Signal) which is the position information of the servo, the servo will perform a wrong correction operation according to the incorrect PES. Accordingly, if there is a defect in a burst pattern, this is handled as a defective sector. This defective sector is reassigned to a different place and written there. However, since the number of sectors that can be reassigned is limited and a seek operation must be performed, a reduction in the performance of the HDD results.
FIG. 10
is a figure for explaining the cas
Asano Hideo
Fukushima Yukio
Kakihara Toshio
Ueda Tetsuo
Altera Law Group LLC
Davidson Dau I.
Hudspeth David
International Business Machines - Corporation
LandOfFree
Disk device, track positioning method and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Disk device, track positioning method and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disk device, track positioning method and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2987138