JPH0256784A - Positioning servo system in magnetic disk device - Google Patents

Abstract

PURPOSE:To attain an easy and high accurate head positioning by forming the area of servo data into a perpendicular triangular shape, obtaining a detecting output pulse and executing a servo control due to the difference in a pulse width between the pulse width and a reference pulse width. CONSTITUTION:At the edge part of plural data tracks (n), a servo data area S is formed in a perpendicular triangular shape, the servo data are read by a head H3 and an output waveform (b) is obtained. Next, the maximum value of the voltage changing together with the time of the output waveform is detected by a peak holding circuit, and a peak holding output waveform is obtained. Next, the peak holding waveform is digitally converted by an A/D converter and a pulse P1 is obtained. Next, the pulse width of a reference pulse and the pulse P1 is compared, the difference is obtained, the offtrack quantity is obtained based on the difference and the offtrack quantity is adjusted so as to become minimum.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a head positioning servo system in a magnetic disk drive, and is aimed at easily and highly accurate head positioning adjustment. A servo data area is formed in the shape of a right triangle at the end of the servo data area, a peak hold value of a detection output is obtained by reading out the servo data by a head, and the peak hold value is A/D converted to obtain a detection pulse width. The detected pulse width is compared with a preset reference pulse width to find a difference, an off-track amount is calculated from the difference with reference to a pre-set table, and a control signal is generated based on the off-track amount. The head is positioned based on the control signal.

[Industrial application field]

This invention relates to a head positioning servo system in a magnetic disk device.

The control for positioning the magnetic head to the target track is usually
This is done by a servo system consisting of a head positioner and a positioning circuit. Generally, a voice coil type linear motor, a DC servo motor, etc. are used in the Hesodobojishishina, and the positioning circuit is composed of a speed detection circuit, a position detection circuit, a reference speed generation circuit, etc.

In commonly used servo systems, the servo data area is usually located at the end of the data trunk in the same plane.
As will be described later, this servo data is detected by two heads, and the head positions are controlled so as to minimize the difference between the detected outputs.

[Problems to be Solved by the Prior Art Invention] FIG. 11 is a diagram illustrating a conventional servo data area. In the figure, n+1. n, nl are data tracks, and S is a servo data (shaded area) area. Servo data is
The data is written on data track n in a form shifted by half a length and seven points in the n+1 direction and the n-1 direction, respectively. These two servo data are read out by two corresponding heads H1 and H2, and their detection outputs are compared. When the difference between the two detection outputs is "O", the head position is determined to be correct, and when there is a difference between the detection outputs, the difference is adjusted to "0".

However, since this detection output is an analog waveform at a voltage level, it is difficult to accurately compare the output levels and accurately adjust the difference to 0''.

An object of the present invention is to perform head positioning adjustment easily and with high precision by focusing on the point that adjustment is performed using the difference between the reference pulse width and the detection pulse width in one head, without using adjustment based on the difference in voltage level between two heads. The object of the present invention is to provide a head positioning servo system that can perform head positioning.

[Means and effects for solving the problems] The present invention is a head positioning servo system in a magnetic disk drive, in which a servo system is provided in the shape of a right triangle at the ends of a plurality of data tracks (1+l, n, n-1). forming a data area (S), determining the peak hold value of the detection output by reading the servo data with the head (H3), converting the peak hold value to AID to determine the detection pulse width (Pl);
The detection pulse width and the preset reference pulse width (P)
, calculate the off-track amount (X) from the difference with reference to a preset table, generate a control signal based on the off-track amount, and generate a control signal based on the control signal. The present invention is characterized in that the head is positioned.

〔Example〕

FIG. 1 is a configuration diagram of an embodiment of the present invention. In the figure, n+1. n and n-1 are data tracks as described above. The servo data moves the head H3 in the n+1 direction or n-
A right triangular area S is obtained by erasing the off-track portion of the parallelogram data area formed by moving the data by a distance d in one direction.

FIG. 2 is a diagram illustrating the above-mentioned method of erasing unnecessary portions. Depending on the position of the head H3, the lower half of the parallelogram may be erased or the upper half may be erased.

Erasing is done by moving the track a distance.

FIG. 3 is a diagram showing the servo data area S (hatched area) obtained by the above-described method. n is a data track. As shown in the figure, the direction of the right triangle is head H3.
There are two types available depending on the position, but in reality it is sufficient to use one of them.

FIG. 4 is a diagram explaining this embodiment. Rather than adjusting the output difference due to each voltage level detected from two heads as in the past, the present invention adjusts the difference between the detected pulse width of the pattern obtained by the head detecting servo data and the reference pulse width. It is something to be adjusted. That is, first, as shown in (a), the servo data area S of track n is read by the head H3 to obtain the output waveform (b). Next, each maximum value of the voltage that changes over time in this output waveform is detected by a peak hold circuit (not shown) to obtain a peak hold output waveform shown in (C).

Next, this peak hold output waveform is digitally converted by an A/D converter to obtain a pulse P1 as shown in (d).

On the other hand, a reference pulse that serves as a reference when on-track is provided in software in a control section (not shown).

The head positioning servo system of the present invention compares the pulse widths of this reference pulse and the detection pulse P1, finds the difference, calculates the off-track amount based on this difference, and adjusts the off-track amount to minimize it. be.

FIGS. 5(a) and 5(b) are diagrams illustrating the difference in pulse width. In (a), the detection pulse P1 and the reference pulse P
Let the difference be y. In (b), the vertical axis is the pulse width difference y, and the horizontal axis is the off-track amount x. The positive side of y is when the width of the reference pulse is wider than the width of the detection pulse, and the negative side is the opposite case. A table defining the relationship between the difference y and the off-track amount x as shown in (b) is prepared in advance in the memory of the control unit, and the off-track amount is calculated from the difference y with reference to this table. Based on this off-track amount, a predetermined control signal (not shown) is generated from the control section to adjust the head position to the normal digit.

Note that this table has values determined in advance from design values for head and track positioning.

FIG. 6 is a diagram illustrating another embodiment of the present invention. In this case, the head H3 is initially moved downward by a distance d,
It is further moved upward by the same distance d. As a result, a fan-shaped servo data area as shown in the figure is formed. Unnecessary portions within this area that protrude from the track are erased by moving the track by a distance as shown in FIG.

FIG. 8 shows the servo data area formed in this way, which has two forms depending on the position of the head.

FIG. 9 is a block diagram of a method according to another embodiment.

Similarly to the above-mentioned Figure 4, the head reads the servo data (a), obtains its output waveform (b), calculates the peak hold output (c) from this waveform, performs A/D conversion, and generates the detection pulse (d). ). In this case, since there are two peak hold output waveforms, the pulse width is the interval from the rise of the previous peak hold waveform to the rise of the subsequent peak hold waveform, as shown in the figure. This detection pulse is compared with the reference pulse in the same manner as described above to calculate the amount of off-trunk, and based on this, a control signal is generated to control the positioning of the head.

FIG. 1θ is a basic flowchart of the head positioning servo system of the present invention. First, as described above, the head is moved to form a servo data area in the form shown in FIG. 3 or FIG. 8 (1). Next, the servo data is read at the current position of the head (2), the peak hold value of the detected output is determined (3), and this value is A/D converted to obtain the pulse width of the detected output (4). Next, compare the width of the preset reference pulse and the detected pulse 5), and if there is a difference in pulse width (6), calculate the off-track amount from the difference in pulse width with reference to the preset table. 7), and generates a control signal for moving the head based on this off-track amount (8).

Using the head position adjusted by this control signal, the servo data is read again to confirm the adjustment. - On the other hand, if there is no difference compared with the reference pulse (9), the head position is not adjusted and the control ends.

〔Effect of the invention〕

As explained above, the present invention makes the servo data area in the shape of a right triangle, and performs servo control based on the difference in pulse width from the reference pulse width, rather than the conventional servo control method based on the difference in voltage level, which is easy and convenient. Highly accurate head positioning adjustment is possible.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention. FIG. 2 is a diagram illustrating erasure of an unnecessary portion of the servo data area of FIG. 1. FIG. 3 is a servo data area of an embodiment of the present invention. Figures 4(a) to (d) are diagrams explaining the procedure of an embodiment of the present invention. Figures 5(a) and (b) are diagrams explaining the pulse width difference and off-track amount. FIG. 6 is a configuration diagram of another embodiment of the present invention, and FIG.
FIG. 8 is a diagram illustrating a servo data area according to another embodiment of the present invention. FIGS. FIG. 10 is a basic flowchart of the present invention, and FIG. 11 is a diagram explaining the procedure of another embodiment. (Explanation of symbols) n+1. n, n l...Data trunk, Hl, H
2, H3...Head, S...Servo data area, P, PI...Pulse width, y...Difference in pulse width, X...Off-track amount・Explaining the conventional servo data area 1. Configuration diagram of an embodiment of the present invention 1. Implementation of the present invention - Explanatory diagram of the POD data process Figure 3. Explanation of erasing unnecessary parts of the read servo data area Fig. 4 An explanatory diagram of the procedure of an embodiment of the present invention Fig. 4 An explanatory diagram of the pulse width difference and off-track amount Fig. An explanatory diagram of erasing unnecessary portions of the servo data area Fig. Other embodiments of the present invention Servo data FIG. 8 is an explanatory diagram of the area. FIG. 9 is an explanatory diagram of the procedure of another embodiment of the present invention. FIG. 9 is a basic flowchart of the present invention.

Claims (1)

[Claims] 1. A servo system for head positioning of a magnetic disk device, in which a servo data area is formed in the shape of a right triangle at the end of a data track, and the peak hold value of the detection output when the servo data is read out by the head is determined. A/D convert the peak hold value to determine the detected pulse width, compare the detected pulse width with a preset reference pulse width to determine the difference, and refer to a preset table to determine off-track from the difference. A head positioning servo system, characterized in that: a control signal is generated based on the off-track amount; and the head is positioned based on the control signal.