Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1999-10-06
2003-03-18
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S077080
Reexamination Certificate
active
06535348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a servo control method and an information storage device, and, more particularly, to a servo control method and an information storage device in which positional information is detected in accordance with servo information including a plurality of positional regions having different phases.
Based on the servo information stored on a magnetic disk in advance, a magnetic disk device detects displacement of a scanning head, so that tracking control can be controlled to perform information reproduction in a desired position.
2. Description of the Related Art
FIG. 1
is a block diagram of a conventional magnetic disk device.
The conventional magnetic disk device
1
comprises a magnetic disk
2
, a spindle motor
3
, a magnetic head
4
, a head arm
5
, a voice coil motor (VCM)
6
, a head amplifier
7
, an A/D converter
8
, a servo circuit
9
, drivers
10
and
11
, a modem circuit
12
, and an interface circuit
13
.
The magnetic disk
2
is secured by a rotation axis
14
of the spindle motor
3
, and is rotated by the spindle motor
3
. The magnetic head
4
faces the magnetic disk
2
. The magnetic head
4
magnetizes the magnetic disk
2
in accordance with a recording signal supplied from the head amplifier
7
, thereby recording information.
The magnetic head
4
also outputs an electric current in accordance with a variation in magnetization of the magnetic disk
2
, thereby outputting a reproduction signal. The magnetic head
4
is secured at an edge of the head arm
5
.
The other edge of the head arm
5
is connected to the VCM
6
via a rotation axis
15
. The VCM
6
oscillates the head arm
5
in the radial direction of the magnetic disk
2
. As the head arm
5
is oscillated by the VCM
6
, the magnetic head
4
is moved in the radial direction of the magnetic disk
2
so as to trace a desired track on the magnetic disk
2
.
The magnetic head
4
is connected to the head amplifier
7
. The head amplifier
7
amplifies a recording signal supplied from the, A/D converter
8
, and sends the amplified recording signal to the magnetic head
4
. The head amplifier
7
also amplifies a reproduction signal detected by the magnetic head
4
, and sends the amplified reproduction signal to the A/D converter
8
.
The A/D converter
8
converts the recording signal supplied from the modem circuit
12
into an analog signal, and sends it to the head amplifier
7
. The A/D converter
8
also converts the reproduction signal amplified by the head amplifier
7
into a digital signal.
The modem circuit
12
modulates information supplied from the interface circuit
13
, and sends it as the recording signal to the A/D converter
8
. The modem circuit
12
also demodulates the reproduction signal supplied from the A/D converter
8
into the original information. The interface circuit
13
exchanges signals with another device connected to the magnetic disk device
1
.
The servo circuit
9
receives the reproduction signal from the A/D converter
8
, and detects the positional difference between the magnetic head
4
and the desired track in accordance with servo information contained in the reproduction signal. The servo circuit
9
then generates a servo control signal in accordance with the positional difference, and sends the servo control signal to the driver
10
. The driver
10
controls the VCM
6
in accordance with the servo control signal transmitted from the servo circuit
9
. The servo circuit
9
also controls the spindle motor
3
through the driver
11
.
The servo information to be detected by the servo circuit
9
is recorded on the magnetic disk
2
in advance.
FIG. 2
shows a format of the conventional magnetic disk
2
.
On the magnetic disk
2
, pieces of servo information SB are formed radially from the rotation axis
14
of the spindle motor
3
. Data is recorded between the pieces of servo information SB. Tracks Tr are formed concentrically with the rotation axis
14
of the spindle motor
3
.
FIG. 3
shows a track format.
The servo information SB and a data region D alternately appear on each of the tracks Tr, as shown in FIG.
3
. Sixty to eighty pieces of servo information SB are arranged on each of the tracks Tr.
FIGS. 4A
to
4
E show a servo information format.
FIG. 4A
shows a pattern of the servo information SB, and
FIGS. 4B
to
4
E show reproduction signal waveforms of the tracks Tr
0
to Tr
3
.
The servo information SB consists of three positional regions “even
1
”, “odd
1
”, and “even
2
”.
In the positional region “even
1
”, if the phase of the signal pattern is set at 0° on the track Tr
0
, the phase is +90° on the track Tr
1
, +180° on the track Tr
2
, and +270° on the track Tr
3
. The phase is back at 0° on the track Tr
4
.
In the positional region “odd
1
”, if the phase of the signal pattern is set at 0° on the track Tr
0
, the phase is −90° on the track Tr
1
, −180° on the track Tr
2
, and −270° on the track Tr
3
. The phase is back at 0° on the track Tr
4
.
In the positional region “even
2
”, if the phase of the signal pattern is set at 0° on the track Tr
0
, the phase is +90° on the track Tr
1
, +180° on the track Tr
2
, and +270° on the track Tr
3
. The phase is back at 0° on the track Tr
4
.
As a result, the tracks Tr can be identified in accordance with the phase difference in the positional regions “even
1
”, “odd
1
”, and “even
2
”.
FIG. 5
shows an operation of the conventional magnetic disk device. As shown in
FIG. 5
, when the detected phase difference of the positional regions “even
1
”, “odd
1
”, and “even
2
” is 0°, the tracks Tr
0
, Tr
2
, and Tr
4
can be identified. When the detected phase difference of the positional regions “even
1
”, “odd
1
”, and “even
2
” is 180°, the tracks Tr
1
, Tr
3
, and Tr
5
can be identified.
The servo circuit
9
detects the phase difference of the reproduction signals of the positional regions “even
1
”, “odd
1
”, and “even
2
” so as to detect the position of the head, i.e., the track being scanned by the head.
FIG. 6
shows an operation of the conventional magnetic disk device. The servo circuit
9
calculates the position (Pos) of the head from the formula:
Pos=(Pe
1
, Pe
2
)−Po
1
wherein Pe
1
, Pe
2
, and Po
1
are phase differences between detection signal and a predetermined track in the positional regions “even
1
”, “odd
1
”, and “even
2
”, respectively, and (Pe
1
, Pe
2
) indicates the average value between Pe
1
and Pe
2
.
As shown in
FIG. 6
, when the phases of the vectors e
1
, o
1
, and e
2
are all 0°, the phase of the position of the head is 0°. Accordingly, it can be judged that the head is scanning the reference track When the head is scanning the track Tr
1
, which deviates from the reference track Tr
0
by one track, the phase of the vector e
1
is +90°, the phase of the vector o
1
is −90°, and the phase of the vector e
2
is +90°. Accordingly, the phase difference of Pos is +180°, and it can be judged that the head is situated on the track Tr
1
, which deviates from the reference track Tr
0
by one track.
When the head is scanning the track Tr
2
, which deviates from the reference track Tr
0
by two tracks, the phase of the vector e
1
is +180°, the phase of the vector o
1
is −180°, and the phase of the vector e
2
is +180°. Accordingly, the phase difference of Pos becomes 0°. This cannot be distinguished from the phase difference of the reference track Tr
0
, and the head cannot be judged to be situated on the track Tr
2
.
When the head is scanning the track Tr
3
, which deviates from the reference track Tr
0
by three tracks, the phase of the vector e
1
is +270°, the phase of the vector o
1
is −270°, and the phase of the vector e
2
is +270°. Accordingly, the phase difference of Pos becomes 180°. This cannot be distinguished from the phase difference of the reference track Tr
1
, and the head cannot be judged to be situated on the track Tr
3
.
As described so far,
Kagami Yoshiyuki
Kosugi Tatsuhiko
Fujitsu Limited
Greer Burns & Crain Ltd.
Hudspeth David
Wong K.
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