JPS6247885A - Servo information detection method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Summary] By utilizing the fact that the amplitudes of servo signals A and servo signals B that are relatively displaced from the center of the track are approximately 1/2 of the amplitude of data, the amplitude of the read signal is detect the peak value of the data, and detect the peak value smaller than a specified ratio of the peak value of the data.

Then, the time when this small peak value is detected is determined to be the starting point of servo signal A, and based on this, the difference in successive times of servo signal A and servo signal B is used. Precise positioning by determining and reading the level provides information for control.

[Industrial application field]

The present invention relates to a magnetic disk device using a sector servo method, and more particularly to a servo information detection method for detecting servo information recorded in each sector with a simple circuit configuration and obtaining information for precise positioning of a magnetic head. .

A magnetic disk drive performs seek control to position a magnetic head on a target trunk () and writes/reads desired data. Incidentally, as the capacity of magnetic disks increases, the spacing between tracks on which data is recorded is reduced, and precision is required in the positioning of the magnetic head.

Therefore, in order to accurately position the magnetic head, servo information is recorded for each sector in each track.

FIG. 4 is a diagram explaining the sector servo method.

The points 1'L4z%1 and 2 indicate the center line of the track.

3 is the servo signal A displaced from the center of track 1,
4 is a servo signal B displaced from the center of the track 1 in a direction opposite to that of the servo signal A; Further, 5 is a servo signal B displaced from the center of the track 2 in the opposite direction of the servo signal A.

6 is the data written to track 1, 7 is the data written to trunk 2
This is the data written to. The servo signal A3 to the servo signal B4 or 5 is a servo area, and the data 6 or 7 is a data area, and this total area forms one sector.

When using this sector servo method, it is necessary to reliably detect servo signal A3 and servo signal B4 when positioning on track 1, and servo signal A3 and servo signal B5 when positioning on track 2, and find the level difference between them. However, this detection method needs to be economical.

[Conventional technology]

As a conventional method of detecting sector servo information, (x)
A hole is punched in the magnetic disk medium at the beginning of each sector of a track provided on the hard disk, and this hole is optically detected and determined as the starting position of servo information.

(2) A special pattern is written at the beginning of a servo area provided for each sector of each track or at the beginning of each of a plurality of servo signals, and when this special pattern is read out, it is determined to be the start position of servo information. In this special pattern, for example, a long distance is provided from one magnetization reversal to the next magnetization reversal, which is impossible for data, and the start of servo information is determined by monitoring the time during reading.

[Problem that the invention seeks to solve]

In the method (1) above, holes must be placed mechanically with high precision on the magnetic disk, and an optical detection circuit is also required.

Method (2) requires a complicated servo pattern and a complicated circuit to detect the special pattern.

Therefore, in any case, there is a problem that the servo information detection method is expensive.

In view of these problems, it is an object of the present invention to provide a servo information detection method that can detect servo information using a simple servo pattern and a simple circuit configuration.

That is, by utilizing the fact that the servo signals A and B shown in FIG. The peak values of the data amplitude, the servo signal A amplitude, and the servo signal B amplitude are detected and stored using the timing signal.

Then, the amplitude of the data stored with a delay of one timing time of the sample timing signal, the amplitude of the servo signal, and the peak values of the amplitude of the servo signal B are compared with each other, and a specified ratio of the peak value of the data is determined, for example, 0.7. When a level equal to or lower than double the level is detected, it is recognized as the beginning of servo signal A, and after a predetermined time has elapsed, it is recognized as servo signal B, thereby detecting the level difference between servo signal A and servo signal B, and detecting this level difference. Precise positioning is based on the control.

[Means for solving problems]

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention.

10 is a magnetic head, 11 is a read amplifier that amplifies the data read by the magnetic head, and 12 is the output of the read amplifier 11, the amplitude of the data, the amplitude of the servo signal A, and the servo signal B.
an amplitude detection circuit for detecting each peak value of the amplitude of 13;
Reference numeral 14 denotes a memory circuit that sequentially samples and stores the output of the amplitude detection circuit 12 in response to a sample timing signal input from terminal E, and 14 a memory circuit that stores the output of the memory circuit I3 with a delay of one timing of the sample timing signal.

15 is a coefficient circuit that multiplies the output of the memory circuit 14 by a coefficient;
16 is a comparison circuit that compares the outputs of the coefficient circuit 15 and the memory circuit 13, and 17 is a delay circuit that sends a time delayed by the reading time difference of the servo signal B to the servo signal.

18 is a circuit ↑a that stores the level of the servo signal A from the output of the amplitude detection circuit 12; 19 is a storage circuit that stores the level of the servo signal B from the output of the amplitude detection circuit 12; 20
is a level difference detection circuit that detects the level difference between servo signal A and servo signal B.

21 is activated by the output of the delay circuit 17 to zero the level difference detected by the level difference detection circuit 20, and is activated by the line control circuit 2.
Get the lower address focus from 2 and TI! tM head 1
22 is a precision control circuit that precisely positions the magnetic head 10 on the target track, and 22 is a line control circuit that approximately positions the magnetic head 10 on the target track in response to a seek command input from the terminal.

23 and 24 are drive circuits that respectively excite the excitation phase A and the excitation phase B of the stepping motor 25 by control signals from the line control circuit 22 and the precision control circuit 21; 25 is the magnetic head 10;
It is a stepping motor that moves the .

The storage circuit 13 stores the amplitude level of data and the amplitude levels of servo signal A and servo signal B, respectively, based on the sample timing signal, and the storage circuit 14 stores the amplitude level of data and the amplitude levels of servo signal A and servo signal B, respectively. It is stored with a delay of one timing time of the sample timing signal.

When the comparator circuit 16 detects that the memory circuit 13 has sent out an amplitude level that is less than the specified ratio of the amplitude level sent out by the memory circuit 14, it recognizes that it is the start of the servo signal A, and the memory circuit 18 starts the servo signal A at this timing. memorize the amplitude level of

Furthermore, the memory circuit 19 stores the amplitude level of the servo signal B at the timing when the delay circuit 17 sends it out.

The level detection circuit 20 is configured to detect the level difference between the servo signal A and the servo signal B and send it to the precision control circuit 21.

[Effect]

With the above configuration, the precision control circuit 21 controls the stepping motor 25 based on the level difference between the servo signal A and the servo signal B so as to reduce this level difference to zero, thereby precisely controlling the magnetic head 10. can be positioned in the desired trunk.

〔Example〕

In Figure 1, a seek command is sent from the terminal to the line control circuit 2.
2, the line control circuit 22 sends signals for driving the A phase and B phase of the stepping motor 25 to the drive circuits 23 and 24, respectively, based on the address of the target trunk.

FIG. 3 is a diagram illustrating the stepping motor drive system.

Current iA flowing through the A phase of the stepping motor 25 on the vertical axis
Assuming that current iB flows in phase B and current iB, and the horizontal axis represents the position of the magnetic head, in the normal system, currents with a phase shift of 90 degrees flow as shown by the dotted line. In this example, as shown by the solid line,
It uses a microstep method that uses sawtooth waves.

That is, when iA is a forming current value, for example, I ampere, flowing to the + side, iB is, for example, when I ampere is flowing, the magnetic head is positioned at the 0th track, iA increases to the + side, and then decreases. Ampere, iB from one side to + side I
When the amperage is reached, the magnetic head is positioned on the first track.

Further, iB increases to the + side and then decreases to ■ ampere, and when iA reaches one ampere from the + side, the magnetic head is positioned at the second trunk.

Next, iA increases and then decreases to ■ ampere, and when iB reaches from the + side to ■ ampere,
The magnetic head is positioned on the third track, iA becomes I ampere on the + side from one side, iB increases and then decreases, and when it reaches ■ ampere, the magnetic head is positioned on the fourth track.

As described above, the step motor 25 is supplied with drive current,
The magnetic head 10 is roughly positioned on the target track. The magnetic head 10 reads data written in each sector, servo signal A, and servo signal B from the track.

FIG. 2 is a time chart explaining the operation of FIG. 1.

For example, if the magnetic head 1o is positioned on track 1 in FIG. 4, the read signal amplified by the read amplifier 11 has an amplitude of 30
Subsequently, the amplitude 31 obtained by reading the servo signal A, the amplitude 32 obtained by reading the servo signal B, and the amplitude 33 obtained by reading the data 6 are obtained.

The reason why the amplitude 31 of the servo signal is smaller than the amplitude 32 of the servo signal B is because the positioning accuracy of the magnetic heel 10 is insufficient and is shifted toward the servo signal B4 side.

The amplitude detection circuit 12 detects the peak value of the data amplitude 3o, the peak value of the amplitude 31 of the servo signal A, and the peak value of the amplitude 32 of the servo signal B from the output of the read amplifier 11, as shown in the amplitude signal of FIG. , and sent to the memory circuits 13, 18, and 19.

As shown in the sample timing signal in FIG. 2, the storage circuit 13 stores the peak value of the amplitude signal in FIG. 2 sent out from the amplitude detection circuit 12 in response to the sample timing signal input from the terminal E. Therefore, the output of the storage circuit 13 is a waveform corresponding to the peak value of the amplitude signal at the time when the sample timing signal is sampled, as shown in the storage signal (2) in FIG.

Since the memory circuit 14 stores the memory signal (2) sent out by the memory circuit 13 with a delay of one timing of the sample timing signal, its output becomes as shown in the memory signal (2) in FIG.

The coefficient circuit 15 multiplies the amplitude 30 of the data by a coefficient to increase the specified ratio, for example, 0.7 times.

Therefore, the output of the memory circuit 14, that is, the specified ratio of the memory signal ■, and the output of the memory circuit 13, that is, the memory signal
6, and when the peak value of the storage signal ■ becomes small, the servo timing signal ■ is sent to the storage circuit 18, as shown in FIG. The level will be memorized.

After a predetermined time, that is, the time difference between the servo signal A and the servo signal B that is determined at the time of writing the servo signal, the delay circuit 17 outputs the servo timing signal as shown in FIG.
The servo timing signal (2) is sent to the storage circuit 19, and the level sent by the amplitude detection circuit 12 at this time is stored.

The level detection circuit 20 compares the stored signals 1 and 2 stored in the storage circuits 18 and 19 as shown in FIG. 2, detects the level difference, and sends it to the precision control circuit 21. The precision control circuit 21 is operated by the servo timing signal ■ sent by the delay circuit 17, and since the storage signal ■ is larger than the storage signal ■, it sends a drive signal to the drive circuits 23 and 24.
Finely adjust iA and iB shown in Figure 3, and record the memory signals ■ and ■.
control so that they are equal.

〔Effect of the invention〕

As explained above, the present invention can detect servo information using a simple servo pattern and with a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention, FIG. 2 is a time chart explaining the operation of FIG. 1, and FIG.
The figure is a diagram for explaining the skipping motor drive system, and FIG. 4 is a diagram for explaining the sector servo system. In the figure, 1.2 is the track, 3 is the servo signal A, and 4.5
is a servo signal B, 6 and 7 are data, 10 is a magnetic head, 11 is a read amplifier, 12 is an amplitude detection circuit,
13.14.18.19 is a memory circuit, 15 is a coefficient circuit,
16 is a comparison circuit, 17 is a delay circuit, 2
0 is a level difference detection circuit, 21 is a precision control circuit, 22
23 and 24 are a line control circuit, 23 and 24 are drive circuits, and 25 is a stepping motor. half 3 mouths

Claims (1)

[Scope of Claims] A sparse control means (22) for approximately positioning the magnetic head (10) on a target track, a first servo signal and a second servo signal that are displaced from the track center written in each sector of each track.
Precision control means (21) that reads the servo signal of the first and second servo signals, detects the positional error of the magnetic head (10) from the track center from the difference between the peak values of the first and second servo signals, and performs precise positioning control. Detection means (1) for detecting the peak value of the amplitude of the read signal
2), a first storage means (13) for storing the peak value detected by the detection means (12) using a sample timing signal; and a first storage means (13) for storing the peak value detected by the detection means (12) according to the sample timing signal. A second storage means (14) stores the output with a delay of one timing time, and the output of (13) of the first storage means is stored in the second storage means (14).
Comparing means (15, 16) for detecting that the output of 14) is smaller than a specified ratio and sending out a servo timing signal; and based on the servo timing signal sent by the comparing means (15, 16), The precision control means (
21) A servo information detection method characterized by comprising means (17, 18, 19, 20) for supplying to the servo information.