JPH02246064A - Head positional deviation correcting method - Google Patents

Abstract

PURPOSE:To easily detect the positional deviation of a servo track when write is performed on the servo track with high accuracy and to perform correction for the positional deviation by calculating the aberration correction value of the servo track with a specific condition. CONSTITUTION:Four servo patterns A-D having two track width are arranged by shifting their phases by every track width. At such a case, simultaneous demodulation are performed on the value XN of position error signals obtained from an (N-1)th servo track and an Nth track, and the value XN+1 of the position error signals obtained from the Nth track and an (N+1)th track. And the positional deviation correction value XN+1' of the (N+1)th track can be calculated by equation XN+1'=XN+XN'-XN+1-Xo from the deviation correction value XN' to correct deviation between a desired write position and an actual write position for the Nth track, the values XN and XN+1 of the position error signals, and a reference track interval Xo. Thereby, the deviation correction of the servo track can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a highly accurate head positioning control method for a magnetic disk device.

[Conventional technology]

In head positioning control of a magnetic disk device, a magnetic position scale is written on a specific disk medium for servo or a part of the disk medium on which data is written, and head positioning is controlled based on this magnetic position scale. A typical position scale is one in which two tracks with different patterns, for example a white pattern and a black pattern, are arranged alternately in the radial direction of the disk medium, and is the position where the amplitudes of the signals reproduced from the two tracks are equal. is the reference position for head positioning.

The desired characteristics of a servo track written with a magnetic position scale are that the track width is equal and it provides a perfectly circular reference position, so writing the pattern on the servo track is done using a laser after the disk media is mounted. This is performed while positioning the head with high precision using an external scale such as a positioning device.

However, since there are mechanical vibrations in the rotating bearing that supports the disk medium, the gimbal that supports the head, the actuator, etc., when writing patterns to the servo track, these mechanical vibrations are transferred and synchronized with the rotation. This causes a misalignment.

The head position misalignment correction method, which is attracting attention as the track density of magnetic disk devices increases, is a method that measures and stores the positional misalignment of this servo track in advance, and then reproduces it from the servo track during actual head positioning control. This is a control method that can provide a perfect circular reference position signal with the same track width regardless of the positional deviation of the servo track by correcting the value of the position signal by adding the stored positional deviation correction data.

[Problem to be solved by the invention]

However, in many of the patent documents related to the above-mentioned positional deviation correction, although the method of storing and holding positional correction data is disclosed in detail,
As typified by Japanese Patent No. 8679, a method for calculating a position correction value only discloses that "the servo head is positioned sufficiently accurately and the positional deviation of the servo track is measured."

The present invention has been made in view of these points, and its purpose is to calculate the amount of positional deviation of a servo track with high precision without using external length measuring means such as a laser positioning system. The purpose is to provide a method.

[Means to solve the problem]

In order to solve such problems, the first invention of the present invention provides a position error signal value XN obtained from the N-1st servo track and the Nth servo track, and The value X of the position error signal obtained from the th servo track. , , and simultaneously demodulates and corrects the deviation between the desired writing position and the actual writing position regarding the Nth servo track
, the positional error signal value XN+XH+1 and the reference track interval X0, the positional deviation correction value XN,' of the N+1st servo track is calculated as XN+1' = XN+XN - XN+l X(1).

Further, the second invention of the present invention has a multi-head consisting of at least two head elements arranged with a one-track interval, and a first The value of the position error signal X (N) l obtained through the head element of
The value of the position error signal obtained through the head element X(1
41) A positional deviation correction value XN' that simultaneously demodulates I and corrects the deviation between the desired writing position and the actual writing position regarding the Nth servo track and the position error signal value X (N) In, X ( From Nil□, calculate the positional deviation correction value X N + 1' of the N+1st servo track as Xe + * + -X (N) t + XN -X
It is calculated as <Ni+>2.

[Effect]

In the head position deviation correction method according to the present invention, each track width has the same value.

〔Example〕

FIG. 1 shows a diagram explaining the principle of a first embodiment of the first invention of the present invention. Figure 1 (a) shows the arrangement of data tracks (mountain)
(C) shows the arrangement of the servo tracks, and (C) shows the position error signal. In the two-phase sabot system, which is the mainstream of magnetic disk drives,
As shown in FIG. 1(b), A~
The four servo patterns D are arranged with a phase shift of one track width, and these servo patterns are separated by approximately 2
It is configured to play with a servo head having a trunk width.

Writing on the servo tracks is performed in the order of N track, N+1 track, and N+2) rack, and since the width of the head is wider than one track width, the servo tracks are overwritten.

As a result, if there is mechanical vibration when writing to the N+1th servo track, for example, the servo pattern D is written in a state shifted from the reference position by ΔD, as shown by the dotted line in the figure. In this case, if the servo head is positioned in the SH3 state using servo patterns B and D, the servo head will be misaligned with respect to the N+1st data track.

Therefore, the deviation (-X□,') from the desired writing position of the N+1th servo track is measured after writing to the servo track, and when controlling the positioning of the servo head as shown in the state indicated by SH3 in Fig. 1. , the deviation of the N+1st servo track from the desired writing position (Xl-1'
) is corrected to a new position error signal (XM+I+XN
If the positioning of the head is controlled based on the reference point , or '), the servo head will follow the desired position. Further, in the position error signal group corrected in this way, as shown in equation (1), the values of adjacent position error signals are separated by the reference track interval X0 regardless of the location.

(XH+XN') (XN, I+XN or +')=X
o... (1) For example, if the deviation (XN') of the Nth servo track from the desired writing position is known, position the servo head as shown in 5) 12 in Figure 1 and set the position. By simultaneously reproducing the error signals XH, xN, and l, the deviation correction amount (XN+1') of the position error signal XH+H is calculated.
can be obtained as shown in equation (2).

X1+1' -Xs+ Xs XN+
t-Xs, that is, the value XN of the position error signal obtained from servo patterns A and C (see characteristic msi) and the value Xw-t of the position error signal obtained from servo patterns B and D.
(See characteristic line S2) to position the servo head as SH2, and in this state, the two position error signals XN
. Furthermore, the value of X on line LM is Xi+XN
The value of X on 1 line L N * 1 is XH + s + X
N+1'.

By using this method to detect and correct positional deviations between servo tracks, the servo tracks can be
This is equivalent to writing everything in parallel with the track as a reference. Furthermore, if we perform learning control to obtain a perfect circle position reference at the 0 track and then determine the positional deviation correction value for all tracks, we can see that all servo tracks have been written in a perfect circle. become equivalent. That is, according to this embodiment, the servo system of the magnetic disk drive can always provide a highly accurate position error signal regardless of the writing accuracy of the servo track writer.

However, in this example, it is important that the detection sensitivity of the position error signal (the slope of characteristic line Sl, 32) does not change even when the servo head is offset. It is desirable to use an unchanging medium as the servo surface.

FIG. 2 shows a control circuit to which the first embodiment of the first invention is applied. In FIG. 2, l is an inverting amplifier, 2 is an adder, 3 is a subtracter, and 4 is a reference signal generation circuit. , 5 is a missing number, 6
is an A/D converter, 7 is a circulating memory, 8 is a microprocessor, 9 is a positional deviation correction data storage circuit, and lO is a D/A
Converter, 11 is adder, 12-19 are missing numbers, 20-23
is a selector.

The position error signal used for positioning control of the servo head is
As shown in Fig. 2, there are two types of signals demodulated from servo patterns A, C, B and D (signals shown in characteristic lines S1 and 82 in Fig. 1), a and b, which are used for normal head positioning control. In this case, a selector 20 operating according to a desired track address selects one of the two position error signals, including its polarity, and the head is positioned with the zero point of the position error signal as the target. On the other hand, in detecting the positional deviation correction value in this embodiment, head positioning control is performed using both of the two simultaneously reproduced positional error signals. Align the slopes of the two position error signals a and b so that the changes in signal amplitude are equal, and
The adder 2 generates a sum signal (a1+bl)/2 of the position error signal values a1 and bt, outputs it as a position signal m for positional deviation detection, and uses it for head positioning control. In this case, by generating an offset DC voltage from the control microprocessor 8 to the D/A converter 10 through the circulating memory 7 and switching the selector 22 while gradually offsetting it, the normal on-track control can be changed. It is possible to smoothly shift to off-track control for detecting positional deviation.

When the servo head is controlled off-track in this way, the servo head is positioned at an intermediate position between the zero points of the two position error signals that are originally positioned. In this state, two position error signals are being reproduced at the same time, and the subtracter 3 produces the head state vR8H1 and the state SH3 in FIG.
A positional deviation is detected, and a reference signal corresponding to the reference trunk interval XO generated from the reference signal generation circuit 4 is further subtracted to obtain a positional deviation correction signal n. This positional deviation correction signal n is digitized through an A/D converter 6, and taken into a rotating memory 7 in synchronization with the rotation of the disk. Thereafter, the data is taken into the microprocessor 8, added to the position correction data of N tracks read from the position correction data storage circuit 9, and stored in the position correction data storage circuit 9 as position correction data of the N+1) rack. Note that the position correction data is stored without using the position correction data storage circuit 9.
The disk medium itself can also be used, as disclosed in Japanese Patent Application No. 63-287581.

By repeating the above operation while advancing the servo head by one track, positional deviation correction values for all tracks can be calculated.

During actual head positioning control, the position correction data taken out from the position correction data storage circuit 9 is transferred to the orbiting memory 7, and converted into analog data through the D/A converter 10 in synchronization with the rotation of the disk medium. , adder 11
is added to the position error signal reproduced from the servo head by. Then, the selector 22 outputs the positioning control signal p. In this way, the signal processing for positional deviation correction in this embodiment is extremely simple.

FIG. 3 shows a diagram explaining the principle of the second embodiment of the first invention. Figure 3+8) shows the arrangement of data tracks, (b) shows the arrangement of servo tracks, and (C) shows the position error signal. is written over three track widths. In addition, this is reproduced by a servo head having a core width of about 3 tracks, and a position error signal as shown in Fig. 3 is reproduced (see characteristic lines 83 to S5). Since the head of
Unlike the illustrated embodiment, two adjacent position error signals can be simultaneously reproduced in a normal on-track state.

For example, the state of positioning on the N track of data 5) 1
4, the position error signal at the N+1 track can be reproduced, or the position error signal at the N+2 track can be reproduced by the MSH 5, which has been positioned at the data N+1 track, and used for positional deviation detection.

Therefore, no special control processing is required to detect positional deviation. In addition, in Fig. 3, the servo head detects three positional error signals in each state, but any two adjacent This signal is used to correct head position deviation.

FIG. 4 shows a control circuit to which the second embodiment is applied. In FIG. 4, the same or equivalent parts as in FIG. 2 are given the same reference numerals. In this circuit, the position signals a, b, and c for spade positioning control are sent by the selector 23a, and the position signals a # , b I , and c for positional deviation detection are sent by the selector 23a.
' is always selected by the selector 23b, and in the on-track state, the subtracter 3 always outputs a positional deviation signal.

This signal processing is similar to that explained in FIG. 2, and its explanation will be omitted here.

FIG. 5 shows a principle explanatory diagram of an embodiment of the second invention of the present invention. In this embodiment, a two-phase servo system similar to that in FIG. 1 is used for the servo pattern, and the servo head has two heads. A multi-head with elements arranged at intervals equal to the track width is used. The core width of the two Herad elements is approximately 2 track widths in the servo surface servo system by applying the two-phase servo system, and approximately 1 track width in the data surface servo system. In addition, in order to effectively utilize the two head elements even after positional deviation detection, one head element is dedicated to the servo with a core width of approximately 2 tracks, and the other head element is dedicated to the servo with a core width of approximately 1 track. A dedicated configuration is effective, and if the reproduction sensitivity of the position error signal from each head element is adjusted to be equal when detecting positional deviation, it is possible to use the two-phase servo method even with the data surface servo method. This enables highly accurate positioning control.

FIG. 5 shows a case where the servo surface servo method is applied, in which two head elements 5HI1.5H12 having a core width approximately twice the track width and arranged at an interval equal to the track width are used.
A servo head 5H10 consisting of the following is used. Then, the head element 5H1 connects the Nth servo track and the N+
The Nth position error signal from the first servo track (
The head element 5H12 simultaneously demodulates the N+1st position error signal (signal indicated by characteristic line S6) d from the N+1st servo track and the N+2nd servo track (signal indicated by characteristic line S7).

The servo pattern arrangement of this embodiment is exactly the same as that of the embodiment shown in FIG. 1, but when reproduction is performed using head elements 5H1 and 5H12, the gap becomes 0 as shown in equation (3).

(X(□l)l + ) is known, the apparatus error signal X(H,
From the device error signal X□++2□ composed of I)l and the head element 5H12, the deviation correction amount (xs-z') of the position error signal Xnet can be obtained as shown in equation (4).

Xゎ! '=X(N.+z+XN*I X engineering,!□・
(4) The positional deviation of the servo pattern is determined from the difference between the positional error signals demodulated from the two head elements 5H1 and 5H12 in this manner.

In this example, two position error signals X(N.1).

Since both Xoi+z> are detected in the original head positioning state, even if the electromagnetic conversion characteristics locally change due to a medium defect or the like, there is no effect at all. In other words, since the positional deviation of the servo track can be detected by considering changes in the electromagnetic conversion characteristics of the medium in advance, there is no need to require a medium with excellent electromagnetic conversion characteristics for the servo surface.
It is possible to achieve positioning control with unprecedented precision.

FIG. 6 shows a control circuit to which the second embodiment of the invention is applied. In the same figure, the same or equivalent parts as in FIG. 4 are given the same reference numerals. Two phases are each reproduced from 5H1 and 5H12, and the selector 23 aligns the inclinations of the position error signals de with respect to the moving direction of the head. Then, the position error signal d demodulated from the head element 5H11 (signal shown by the characteristic line S6) is provided for head positioning control, and the position error signal e demodulated from the head element 5H12 (signal shown by the characteristic line S7) is used for positioning control. Used for shift detection. In the case of this embodiment, since the head elements 5)(11 and 5H12 are deviated from each other by the reference track width in advance, the servo pattern can be directly determined from the difference between the device error signals Xll+11 and X2.2, which are composed of the two head elements. This embodiment is characterized in that it not only does not require off-track control to detect positional deviations, but also is completely unaffected by unevenness in the electromagnetic conversion characteristics of the servo medium.

〔Effect of the invention〕

As explained above, the present invention sets the positional deviation correction value X If + 1' of the N+1st servo track to XN+1
' = XN + XN XN + 1 xll or XO, ''' Detects easily and accurately,
This has the effect of being able to correct positional deviations. As a result, regardless of the writing accuracy of the servo track writer,
Highly accurate head positioning control can be achieved. In addition, there is no need for external length measurement means such as a laser positioning system.
Productivity is extremely high because the positional deviation correction value can be measured by the positioning control system itself.

The present invention is applicable not only to the servo surface servo system but also to the data surface servo system represented by sector servo, etc., and its effects become greater as the track density improves.

[Brief explanation of drawings]

FIG. 1 is a principle explanatory diagram for explaining a first embodiment of the first invention of the present invention, FIG. 2 is a control circuit diagram to which the first embodiment of the first invention is applied, and FIG. The figure is a principle explanatory diagram for explaining the second embodiment of the first invention, FIG. 4 is a control circuit diagram to which the second embodiment of the first invention is applied, and FIG. 5 is a diagram of the control circuit to which the second embodiment of the first invention is applied. A principle explanatory diagram for detailed explanation of the second invention,
FIG. 6 is a control circuit diagram to which the second embodiment of the invention is applied. 1... Inverting amplifier, 2, 11... Adder, 3...
Subtractor, 4... Reference signal generation circuit, 6... A/D converter, 7... Circulating memory, 8... Microprocessor, 9... Positional deviation correction data storage circuit, lO.・・・
D/A converter, 11...adder, 20-23...selector.

Claims (2)

[Claims] (1) In a head positioning control method for a magnetic disk device, the value X_N of a position error signal obtained from the N-1st servo track and the Nth servo track, and the value A position error correction value X_N′ that simultaneously demodulates the position error signal value X_N_+_1 obtained from the position error signal and corrects the deviation between the desired writing position and the actual writing position regarding the Nth servo track, and the position error signal value X_N ,X_N_
+_1 and the reference track interval X_O, the positional deviation correction value X_N_+_1' of the N+1th servo track is determined by X_N_+_1'=X_N+X_N'-X_N_+_1
A head position deviation correction method characterized by calculating as -X_O. (2) A head positioning control method for a magnetic disk device, which has a multi-head consisting of at least two head elements arranged one track apart, and N-
The position error signal value X_(_N_)_1 obtained from the first servo track and the Nth servo track via the first head element, and the value X_(_N_)_1 of the position error signal obtained from the first servo track and the Nth servo track, and
The value of the position error signal obtained from the first servo track via the second head element X_(_N_+_1_)_
2 and the positional error correction value X_N' that corrects the deviation between the desired writing position and the actual writing position regarding the Nth servo track, and the position error signal values X_(_N_)_1, X_(_N_+_1_ )_2 to positional deviation correction value X_N of the N+1st servo track
＿＋＿1′ is X_N＿＋＿１′=X_(＿N＿)＿１＋X_N′−X
A head position deviation correction method characterized by calculating as _(_N_+_1_)_2.