JPH02230570A - Track follow-up controller - Google Patents

Abstract

PURPOSE:To accurately generate a position error signal even when the amplitude value of a servo pattern changes by finding the position error signal by calculating the maximum value of the amplitude value of the servo pattern from a main servo pattern and two sub servo patterns, and eliminating the difference of the amplitude values of the sub servo patterns by the above maximum value. CONSTITUTION:When a magnetic head 1 is positioned at a recording track N, the servo patterns E, A, and B are read sequentially, and after peak values are detected at a read amplifier 3, the amplitude value of the pattern E is held at a peak holding circuit 5, and that of the pattern A at a peak holding circuit 6, and that of the pattern B at a peak holding circuit 7 via a servo pattern discrimination circuit 4. Next, the displacement quantity X of the head 1 from the center line of the recording track N is calculated at an arithmetic circuit 8 based on equation I. In equation, head width is assumed as HW, the head output of the main servo pattern E as Es, and the head output of the sub servo patterns A and B as Ea and Eb. Thereby, it is possible to generate the position error signal accurately without depending on the amplitude value of the servo pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a track following control device for a magnetic head in a magnetic disk device such as a flexible magnetic disk device.

BACKGROUND OF THE INVENTION In recent years, as digital file devices have become larger in capacity, flexible magnetic disk devices have also been required to have higher density and larger capacity as backup devices.

In conventional flexible magnetic disk drives, since the track density is not so high, tracking control of the magnetic head is not required. Positional deviation of the magnetic head from the center line of the recording 1 rack due to the effects of this will degrade the S/N of the reproduced signal, making it impossible to reproduce the recorded signal. 1. Rack tracking control becomes necessary.

Generally, in a magnetic disk drive, in order to perform trunk tracking control, a servo pattern is placed on the 1st rack and a position error signal is generated. This is broadly classified. Servo surface servo has a disk surface on which only servo patterns are written, and is especially used on large magnetic disks.

On the other hand, with data surface servo, a servo pattern is written in the middle of the data, and there are two types: index servo, which has a servo pattern written in only one place per track, and sector servo, which has a servo pattern written in each sector. In the case of equipment, a sector servo is used because a dedicated servo surface cannot be used and the eccentricity is large.

Here, conventional l/rack follow-up control will be explained using a sector servo as an example.

FIG. 4 shows a conventional 11-rank follow-up control device using sector servo. 1 is a magnetic head, 2 is a head amplifier, 3 is a lead amplifier, 4 is a surf pattern discrimination circuit, 5,
6 is a circuit for peak-holding the output of the head amplifier, and has peak bold timing input terminals 51 and 61. 7 is a differential amplifier, and 8 is a control circuit, which has a servo pattern identification signal input terminal 82, a servo pattern detection signal input terminal 83, and a position error signal input terminal 81. Reference numeral 9 denotes a head actuator, which moves the magnetic head 1 in a direction perpendicular to 1 to 1. FIG. 5 also shows the arrangement of zapopakun on the disk.

Next, the operation C of the conventional example described in Section 2 will be explained. In FIG. 4, the signal output from the magnetic head 1 is amplified by the head amplifier 2, and then sent to the read amplifier 3 and the peak hall I.
- Input to circuits 5 and 66. The peak of the signal input to the redo amplifier 3 is detected, output as a binary signal, and input to the ZARHO pattern discrimination circuit 4 which generates a timing signal for peak holding. The servo button discrimination circuit 4 outputs a peak hold timing signal, a servo button identification signal, and a servo pattern detection signal by discriminating the pulse position or pulse frequency.

Furthermore, as shown in FIG. 5, the servo patterns A, B, C, and D are arranged at a position where the center of each servo pattern is separated from the center line of the recording l/rank by a half track pitch. If G is located on the center line of the recording rack N, the amplitude of the output of the head with respect to the servo back of each of G pieces A and B will be equal.

Further, when the magnetic head is displaced from the center line of the recording trunk N, the amplitude of the head output for the servo pattern on the displaced side becomes large, and the amplitude of the head output for the servo pattern on the opposite side becomes small.

Therefore, if we take the difference between the amplitude values of servo patterns A and B, we get
It is possible to obtain a position error signal that changes with respect to the displacement of the magnetic head from the center line of the recording rack N. The peak hole 1' circuit 5 bolds the amplitude value of servo pattern A based on the peak bold timing signal output from the servo pattern discrimination circuit 4, and similarly, the peak hold circuit 6 bolds the amplitude value of servo pattern B based on the peak hold timing signal. hold.

Further, the respective outputs are input to a differential amplifier 7, a difference is taken, and the result is output as a position error signal and input to a control circuit 8. The control circuit 8 controls the position of the head actuator based on the input position error signal, servo pattern identification signal, and servo pattern detection signal, and positions the magnetic head on the recording track N.

(For example, Nikkei Electronics 1987.1.26 N
o. 413) Problems to be Solved by the Invention However, in the above conventional track following control device,
There is a problem in that the magnitude of the position error signal depends on the amplitude value of the servo pattern itself.

That is, in the above example, even if the amount of displacement from the center line of the recording truss of the magnetic head is the same, the servo pattern A
, B, C, and D, the difference between these amplitude values also increases, so that it is detected as if the amount of displacement from the center line had increased. Looking at this from the perspective of the servo mechanism that positions the magnetic head, it means that the conversion gain when converting the amount of displacement from the center line of the magnetic head into a position error signal changes depending on the amplitude value of the servo pattern. This results in deterioration of the positioning accuracy of the magnetic head on the recording track.

The present invention solves these conventional problems,
The purpose of the present invention is to provide an excellent track following control device that can generate accurate position error signals even if the amplitude value of the servo pattern changes due to factors such as the characteristics of the recording medium, the characteristics of the magnetic head, and changes over time. It is something to do.

Means for Solving the Problems In order to achieve the above object, the present invention provides a main servo pattern on the center line of a recording track, and a first and second servo pattern on both sides of the recording track at positions separated by a predetermined distance. A sub servo pattern is provided, a servo pattern discrimination means for discriminating the main servo pattern, the first sub servo pattern and the second sub servo pattern from each other, and a head output for the main servo pattern, the first sub servo pattern and the second sub servo pattern. A means for detecting the head width and an H. ,
When the head output of the main servo pattern is ES, the head output of the first sub-servo pattern is Ea, and the head output of the second sub-servo pattern is Eb, the displacement X of the magnetic head from the center line of the recording track is calculated as follows. and position error signal calculation means for calculating based on the formula.

Effects The present invention has the following effects due to the above structure. That is, the maximum value of the amplitude values of the servo patterns is calculated from the main servo pattern and the two sub-servo patterns, and the difference in amplitude values between the sub-servo patterns is divided by this value to obtain a position error signal. Therefore, it is possible to obtain a position error signal that does not depend on the amplitude value of the servo buck.

Embodiment Hereinafter, a track following control device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.

1 is a magnetic head, and 2 is a head amplifier. A read amplifier 3 detects the peak of the input signal, and has a binary signal output terminal 31. A servo pattern discrimination circuit 4 generates a servo pattern peak hold timing signal, a servo pattern identification signal, and a servo pattern detection signal. 5, 6, and 7 are peak hold circuits that hold the peak value of the output signal of the head amplifier 2, and have peak hold timing signal input terminals 51, 61, and 71 and peak hold signal output terminals 52, 62, and 72. 8
is an arithmetic circuit that calculates a position error signal from the peak hold signals output from the peak hold circuits 5, 6, and 7.

9 is a control circuit, and servo pattern identification signal input terminal 1
23, a servo pattern detection signal input terminal 122, and a position error signal input terminal 121, and outputs a control signal for the head actuator.

10 is a hand actuator. FIG. 2 shows an example of a servo pattern, in which sub-servo patterns A, B, C, and D are placed at positions half a track pitch away from the center line of the recording track, and main servo patterns E and F are placed on the center line of the recording track. A servo pattern is arranged.

Next, the operation of the above embodiment will be explained. A case will be described in which the magnetic head is displaced from the center line of recording 1/rack N within a range where servo patterns A and B can be detected.

In the above embodiment, when the magnetic head is located on the recording track N, the E, A, and B servo patterns are sequentially read by the magnetic head. After the peak position of the reproduced signal is detected by the read amplifier 3, it is input as a binary signal to the servo pattern discrimination circuit 4, and a servo pattern identification signal, a peak hold timing signal, and a servo pattern detection Q signal are generated. When the servo pattern discrimination circuit 4 detects the servo pattern E, it outputs a peak hold timing signal to the peak hold circuit 5, and detects the servo pattern E.
The amplitude value of is held in the peak hold circuit 5. Similarly, the amplitude value of servo pattern A is poled to peak hold circuit 6C, and the amplitude value of servo pattern B is poled to peak hold circuit 7.

The output signals of the peak hold circuits 5, 6, and 7 are sent to the arithmetic circuit 8.
is input.

The arithmetic circuit 8 calculates a position error signal based on these signals, and the relationship between the amplitude value of each Zarbo Pakun and the displacement amount of the head will be explained here. FIG. 4 is a diagram showing how the amplitude values of servo patterns E, A, and B that can be detected when the head is near recording 1/rack N change as the head moves. For example, for the main servo pattern E, the amplitude value is maximum on the center line of the recording track N, decreases as the head moves away from the center line, and becomes zero when the head reaches a displacement amount that no longer traces the servo pattern E. Similarly, for the sub-servo patterns A and B, the amplitude values reach a maximum at a position offset by a half-track pinch from the center line of the recording track N, and decrease as the distance from that position increases. Here, if the position of the center line of the recording track N is the origin, the amount of displacement of the head is represented by X, and the maximum value of the amplitude values of these servo patterns is E0, then the amplitude value E of the main servo pattern E
S can be expressed as follows.

Es Eo ・(H+-IXI)/Hw Similarly, the amplitude values of the sub servo patterns A and B, E1 and E, are E. -EO-(
r-rl. , -xo -X) /H,,Eb -Eo
- (H, -Xo +X)/Hw. Here I]l. , is the width of the magnetic head, and Xo is the distance of the sub-servo pattern from the center line of the recording track.

For example, if the position error signal
Ea 2 Eo -X / H+. +. Maximum amplitude value E. As mentioned above, varies depending on the characteristics of the recording medium and the head. Furthermore, in magnetic disk drives, the relative speed between the head and the recording medium changes between the inner recording track and the outer recording track, so it varies depending on the position of the head. also changes.

On the other hand, in the track following control device of the present invention, the arithmetic circuit 8
In this step, the amount of displacement of the head is calculated using the following arithmetic expression. The numerator part of the denominator formula is the same as the conventional example, but the denominator is 2Es + Eb -E. 2-Eo − (Hw IXI)/Hl,,+
1 2Bo - X/HW 2・EO Therefore, if the calculated head width is I1, then
In this way, the maximum value E of the amplitude value. It is possible to detect the amount of displacement of the head without depending on it at all.

As is clear from the above equation, the factor that changes the conversion gain is the actual head width H. This is only due to the difference in the calculated head width H,1゛.

The control circuit 9 determines the amount and direction of displacement of the magnetic head based on the input position error signal, and outputs a control signal to the head actuator 10 for positioning the magnetic head 1 on the center line of the recording track N.

In this way, according to the above embodiment, the peak hold circuit 5
By effectively utilizing the amplitude value of the main servo pattern to be bolded, there is an advantage that a position error signal can be generated without depending on the amplitude value of the servo pattern.

Effects of the Invention As is clear from the above embodiments, the present invention can be applied regardless of the amplitude value of the servo pattern, which changes depending on the characteristics of the head that changes for each disk drive, the characteristics of the disk, changes over time, or the position of the head on the disk. , it is possible to always detect an accurate position error signal, which is extremely useful.

[Brief Description of the Drawings] Fig. 1 is a schematic block diagram of a track following control device in an embodiment of the present invention, Fig. 2 is a servo pattern diagram in the same device, and Fig. 3 is a head displacement amount and servo button amplitude value. 4 is a schematic block diagram of a conventional track following control device, and FIG. 5 is a servo pattern diagram of the same device. 3... Lead amplifier, 4... Servo pattern discrimination circuit, 5, 6.7... Peak hold circuit, 8... Arithmetic circuit, 9... ...Control circuit.

Claims (1)

[Scope of Claims] A track following control device for controlling the position of a magnetic head with respect to a recording track of a magnetic recording medium, comprising: a main servo pattern on the center line of the recording track; and a predetermined pattern on both sides of the center line of the recording track. a servo pattern discriminating means for discriminating the main servo pattern, the first sub servo pattern and the second sub servo pattern from each other; means for detecting head outputs for the first sub-servo pattern and the second sub-servo pattern; a head width H_w; a head output of the main servo pattern E_s; a head output of the first sub-servo pattern E_a; When the head output of the second sub-servo pattern is E_b, the amount of displacement X of the magnetic head from the center line of the recording track is expressed as: X=H_w・[(E_b-E_a)/2E_s+|E_
1. A track following control device comprising: position error signal calculation means for calculating based on a calculation formula: b−E_a|].