JPS6247884A - Detecting system for servo information - Google Patents

Abstract

PURPOSE:To attain the detection of servo information with a simple servo pattern and a simple circuit constitution by detecting the level difference between two servo signals existing at both sides of the track center and performing the accurate positioning control of a magnetic head based on the detected signal level difference. CONSTITUTION:When a magnetic head 10 is positioned at a prescribed track, the peak holding circuits 12 and 13 hold the amplitudes of both servo signals existing at both sides of the track. Here the circuit 12 has a sufficiently large time constant and holds the level of the peak signal. While the circuit 13 has a small time constant and varies in response to the value of the signal amplitude. A coefficient circuit 14 multiplies the output of the circuit 12 by a prescribed coefficient. Thus the prescribed ratio of the output of the circuit 12 is compared with the output of the circuit 13 by a comparator 15. When the output of the circuit 13 is reduced, the level sent out from the circuit 13 is stored in a storage circuit 17. At the same time, the level sent from the circuit 13 and delayed by the prescribed time through a delay circuit 16 is stored in a storage circuit 18. A precise control circuit 20 controls a stepping motor 24 based on the output difference between circuits 17 and 18.

Description

[Detailed Description of the Invention] [Summary] Taking advantage of 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 beginning of the servo area is detected by a peak hold circuit equipped with a charging/discharging circuit. Then, the servo signal A and the servo signal B are distinguished from each other by using the difference in successive times between the servo signals A and servo signals B, and by reading their levels, information for precise positioning control is provided.

[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 device performs seek control to position a magnetic head on a target track, 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. 5 is a diagram explaining the sector servo method.

Dashed lines 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 track 1 in a direction opposite to that of the servo signal. 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 track 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, (1)
A hole is made in the magnetic disk medium at the beginning of each sector of a track provided on the magnetic 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, servo signal A and servo signal B shown in FIG. Hold the peak value.

Then, when the magnetic head is positioned on the target track by line control, the held peak value is detected and compared with each peak value of the data amplitude, the amplitude to the servo signal, and the amplitude of the servo signal B. Specified percentage of peak value of data,
For example, when a level of 0.7 times or less is detected, it is recognized as the beginning of a servo signal, and after a predetermined time has elapsed, it is recognized as servo signal B, and the servo signal B is converted into a servo signal.
The precision positioning is controlled based on this level difference.

[Means for Solving the Problems] FIG. 1 is a block diagram of a circuit showing an embodiment of the present invention.

10 is a magnetic head, 11 is a read amplifier for amplifying data read by the magnetic head, and 12 is a charging/discharging circuit with a sufficiently large time constant for the reading time of servo signal A and servo signal B shown in FIG. A peak hold circuit 13 is a peak hold circuit having a charging/discharging circuit with a sufficiently small time constant for the reading time of servo signal A and servo signal B shown in FIG.

14 is a coefficient circuit that multiplies the output of the peak hold circuit 12 by a coefficient; 15 is the coefficient circuit 14 and the peak hold circuit 1;
A comparison circuit 16 compares the outputs of servo signals A and B, and a delay circuit 16 sends out a time delayed by the reading time difference between the servo signals A and B.

17 is the servo signal A from the output of the peak hold circuit 13
18 is a storage circuit that stores the level of servo signal B from the output of peak hold circuit 13, and 19 is a level difference detection circuit that detects the level difference between servo signal A and servo signal B.

20 is activated by the output of the delay circuit 16 to zero the level difference detected by the level difference detection circuit 19, and is activated by the line control circuit 2.
a precision control circuit that obtains the lower bits of the address from 1 and precisely positions the magnetic head 10 on the target track;
Reference numeral 1 denotes a line control circuit that approximately positions the magnetic head 10 on a target track in response to a seek command input from a terminal.

22 and 23 are drive circuits that respectively excite the excitation phase A and excitation phase B of the stepping motor 24 by control signals from the line control circuit 21 and the precision control circuit 20; 24 is the magnetic head 10;
It is a stepping motor that moves the .

The peak hold circuit 12 holds the amplitude level of the read data, the peak hold circuit 13 sends out the amplitude level of the data and the amplitude levels of servo signal A and servo signal B, respectively. When an amplitude level less than a specified ratio of the amplitude level to be sent out is detected, it is recognized as the start of servo signal A, and the storage circuit 17 stores the amplitude level of servo signal A at this timing.

Furthermore, the memory circuit 18 stores the amplitude level of the servo signal B at the timing when the delay circuit 16 sends it out.

The level detection circuit 19 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 20.

[Effect]

With the above configuration, the precision control circuit 20 controls the stepping motor 24 based on the level difference between the servo signal A and the servo signal B so as to make this level difference zero.
By controlling the magnetic head 10, the magnetic head 10 can be precisely positioned on the target track.

〔Example〕

In Figure 1, a seek command is sent from the terminal to the line control circuit 2.
1, the line control circuit 21 sends signals for driving the A phase and B phase of the stepping motor 24 to the drive circuits 22 and 23, respectively, based on the address of the target track.

FIG. 4 is a diagram illustrating the stepping motor drive system.

Current iA flowing in the A phase of the stepping motor 24 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,
A micro-stamp method is used to flow sawtooth waves.

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

Further, iB increases to the + side and then decreases to 1 ampere, and when iA reaches I ampere on one side from the + side, the magnetic head is positioned on the second track.

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 1 ampere from one side to the + side, iB increases to one side and then decreases, and when it reaches ■ ampere, the magnetic head is positioned on the fourth track.

As described above, the step motor 24 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 10 is positioned on track 1 in FIG. 5, the read signal amplified by the read amplifier 11 will have 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 A is smaller than the amplitude 32 of the servo signal B is because the positioning accuracy of the magnetic head 10- is insufficient and is shifted toward the servo signal B4 side.

The peak hold circuit 12 has a configuration as shown in FIG. 3, and inputs the output of the read amplifier 11 to the + terminal of the operational amplifier 25, and connects the output of the operational amplifier 25 to one terminal. The output of the operational amplifier 25 is rectified by a diode 26, and based on a time constant formed by a resistor R and a capacitor C, a DC voltage corresponding to the amplitude of the input signal is maintained.

The time constant of the peak hold circuit 12 is sufficiently large, and the second
As shown in peak signal (2) in the figure, the data amplitude level is maintained at 30.33. The peak hold circuit 13 is the same as the circuit shown in FIG. 3, but the time constant formed by the resistor R and capacitor C is small, and as shown in peak signal ■ in FIG. 31, varies depending on the amplitude 32 of the servo signal B and the amplitude 33 of the data.

The coefficient circuit 14 multiplies the amplitude 30 of the data by a coefficient to increase the specified ratio, for example, 0.7 times.

Therefore, the specified ratio of the output of the peak hold circuit 12 and the output of the peak hold circuit 13 are compared in the comparator circuit 15, and when the output of the peak hold circuit 13 becomes smaller, the servo timing signal (■) is sent to the storage circuit 17. The level sent out by the peak hold circuit 13 at this time is stored.

The delay circuit 16 sends the servo timing signal ■ to the storage circuit 18 after a predetermined time, that is, the time difference between the servo signal A and the servo signal B determined at the time of writing the servo signal, is sent to the storage circuit 18, and the peak hold circuit 13 at this time is The level to be sent is memorized.

The level detection circuit 19 compares the hold signal (2) and the hold signal (2) stored in the storage circuits 17 and 18, detects the level difference, and sends it to the precision control circuit 20. The precision control circuit 20 is operated by the servo timing signal ■ sent by the delay circuit 16, and since the hold signal ■ is larger than the hold signal ■, it sends a drive signal to the drive circuits 22 and 23.
Finely adjust iA and iB shown in Figure 4 and set the hold signal ■
Control is performed so that and ■ 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.
FIG. 4 is a circuit diagram showing an example of the peak hold circuit shown in FIG. 1, FIG. 4 is a diagram explaining a stamping motor drive method, and FIG. 5 is a diagram explaining a sector servo method. In the figure, 1.2 is the track, 3 is the servo signal A, and 4.5
is servo signal B, 6 and 7 are data, 10 is a magnetic head, 11 is a read amplifier, 12 and 13 are peak hold circuits, 14 is a coefficient circuit, 15 is a comparison circuit, 16 is a delay circuit, 17 and 18 are storage circuits , 19 is a level difference detection circuit, 20 is a precision control circuit, 21 is a line control circuit,
22 and 23 are drive circuits, 24 is a stamping motor, 25 is an operational amplifier, and 26 is a diode. Stem 22 Pole 4 Same

Claims (1)

[Scope of Claims] A sparse control means (21) 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 (20) 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. and a first peak hold means for holding the peak value of the read signal, which includes a charging/discharging circuit having a sufficiently large time constant with respect to the reading time of the first and second servo signals. (12)
and a second peak hold means (13) for holding the peak value of the read signal, which is equipped with a charging/discharging circuit having a sufficiently small time constant with respect to the reading time of the first and second servo signals; The output of the second peak hold means (13) is
detection means (14, 15) for detecting that the output of the peak hold means (12) is smaller than a specified ratio; and based on the detection result of the detection means (14, 15), the peak value of the first servo signal is determined. and means (16, 17, 18, 19) for detecting the difference between the peak value of the second servo signal and supplying the detected difference to the precision control means (20).