JPH04298867A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To double the position detecting resolution of rough position information and to improve the accuracy of the position detecting at the time of seek action without complicated treatment. CONSTITUTION:The rough information of a servo information having the rough position information and fine position information is composed of six bit cells, and only the last bit cells (a) are written in a position by 1/2 track off in the direction of the track crossing and take different values at every one track width in the direction of the track crossing, and rest bit cell columns (b) are written on the center of the track and form code columns identifying respective adjoining data tracks. When a magnetic head positions just on the center of the 0 track, the rough position information is either 000000 or 000001, but when the magnetic head comes near 1 track on the 0 track the rough position information is read as 000001. When the magnetic head comes nearer the 1 track, the rough position information is 000011. In this manner, the rough position information having different values at every track is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive, and more particularly to the structure of servo information recorded in a servo sector of a sector servo type magnetic disk drive.

0002

2. Description of the Related Art Recent small-sized magnetic disk drives have become extremely high in track density in order to increase storage capacity. For this reason, it is necessary to reduce the positional deviation between the magnetic head and the data track, and the number of sector servo type magnetic disk drives in which head positioning servo information is written within the data recording surface is increasing. Although sector servo type devices have recently become popular, the idea of the sector servo type itself has been around for a long time.
1-131607 ``Transducer Positioning System'' has a configuration similar to recent sector servo type magnetic disk drives.

[0003] Here, a sector servo system for a magnetic disk drive will be explained with reference to the drawings.

FIG. 2 is a diagram showing a data recording surface of the sector servo system, and FIG. 3 is a diagram showing the internal structure of each servo sector in FIG. 2.

In FIG. 2, in the sector servo system, eight servo sectors are drawn per revolution, but in reality there are 32 servo sectors.
It is normal to provide about 64 or so.

Further, in FIG. 3, the servo information of the servo sector is recorded separately into coarse position information for identifying a track and fine position information for detecting the amount of off-track within one track.

The coarse position information is used to detect the current position during a seek and must be able to identify the maximum number of tracks traversed in time from one servo sector to the next. Furthermore, it is necessary to be able to detect the position even between tracks, and a code, typically a Gray code, that differs by one bit from the code string of an adjacent track is used.

[0008] The rough position information is read during seek,
Since seek control is performed based on this, the code must be difficult to detect incorrectly.

[0009] Furthermore, the DC erase before rough position information is
It is used to identify servo sectors and user data sections and to detect the starting point of coarse position information.

0010

In magnetic disk drives of the servo surface servo type, which is different from the sector servo type and has been widely used in the past, the position detection resolution during seek is usually about 1/2 track.

[0011] If the position detection resolution is low, the resolution of the target speed set according to the remaining distance to the target will also be coarse.
Speed control accuracy deteriorates. Furthermore, in sector servo, the speed is estimated from the amount of movement between sectors, so if the position detection resolution is low, the accuracy of the estimated speed value will also be poor.

[0012] Therefore, it is desirable that the sector servo type magnetic disk device be able to obtain at least the same position detection resolution as that of the servo surface servo type.

However, as mentioned above, in the conventional sector servo type magnetic disk device,
Conventional rough position information represented by 607 corresponds to a track address, and the position detection resolution is one track.

Therefore, in the case of conventional sector servo, in order to obtain a resolution of one track or more, it is necessary to judge the position by combining precise position information in addition to coarse position information, which complicates the processing of the microprocessor. , the disadvantage is that the time delay becomes large.

An object of the present invention is to improve the structure of the coarse position information so that a position detection resolution of 1/2 track can be obtained using only the coarse position information, thereby doubling the position detection resolution of the coarse position information compared to the conventional method. By doing so, it is an object of the present invention to provide a magnetic disk device that can eliminate the above-mentioned drawbacks and improve the accuracy of position detection during a seek operation without performing complicated processing.

[0016]

[Means for Solving the Problems] In the magnetic disk drive of the present invention, servo information for moving and positioning a magnetic head to a target position is composed of coarse position information and precise position information, and the servo information is arranged on a magnetic disk. The magnetic disk drive is characterized in that rough position information is configured as described below. (a) Consisting of a plurality of bit cells in the longitudinal direction of the track,
Each bit cell represents a first or second value, thereby forming a binary code string, and the bit cell strings are arranged in alignment with adjacent bit cell strings in the cross-track direction. (b) Only one bit cell in each bit cell string is written at a position off-track by 1/2 track in the cross-track direction, and takes a different value for every track width in the cross-track direction. (c) The remaining bit cell strings other than the one bit cell described in paragraph (b) are written on the track center and identify each data track that is a member of a set of adjacent data tracks. Construct a code string,
Only one bit cell between mutually adjacent bit cell rows takes a different value.

[0017]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing rough position information of a magnetic disk device according to an embodiment of the present invention, FIG. 2 is a diagram showing a data recording surface of the sector servo system, and FIG. 3 is a diagram showing the internal configuration of each servo sector in FIG. 2. It is a diagram.

Here, the sector servo system shown in FIGS. 2 and 3 is as explained in the section of the prior art.

In FIG. 1, the coarse position information consists of 6 bit cells, each bit cell representing 1 or 0. Moreover, they are aligned in the cross-track direction (vertical direction in the figure). Only the last bit cell a is written at a position off-track by 1/2 track in the cross-track direction, and takes a different value for each track width in the cross-track direction.

The remaining bit cell string b is written on the center of the track and constitutes a code string for identifying each adjacent data track. Since it is necessary to be able to detect the position even between tracks, the code string of the adjacent track
Codes that differ only in bits are used. This example uses Gray code.

If the magnetic head is exactly on the center of track 0, the rough position information will be 000000 or 0000.
However, if it is located one track above the 0 track as shown in FIG. 1, the rough position information can be read as 000001. If the magnetic head moves one track closer, the rough position information becomes 000011. In this way, different coarse position information is obtained every 1/2 track, so the position detection resolution is 1/2 track.

[0023] The rough position information of the conventional sector servo is 1/
Bit cell a written with only 2 tracks off track
, the position detection resolution is only one track.

[0024]

As explained above, the magnetic disk drive of the present invention improves the structure of the coarse position information so that a position detection resolution of 1/2 track can be obtained using only the coarse position information. By doubling the position detection resolution of the conventional method, there is an effect that the accuracy of position detection during a seek operation can be improved without performing complicated processing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing rough position information of a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a data recording surface of the sector servo method.

FIG. 3 is a diagram showing the internal configuration of each servo sector in FIG. 2;

[Explanation of symbols]

a Bit cell written with 1/2 track off track

Claims (1)

[Claims] Claim 1: Servo information for moving and positioning the magnetic head to a target position is composed of coarse position information and precise position information, and the servo information is for each data track in at least one data recording surface of the magnetic disk. A magnetic disk device in which information is recorded in a plurality of servo sectors that traverse a servo sector, wherein the rough position information is configured as described below. (a) Consisting of a plurality of bit cells in the longitudinal direction of the track,
Each bit cell represents a first or second value, thereby forming a binary code string, and the bit cell strings are arranged in alignment with adjacent bit cell strings in the cross-track direction. (b) Only one bit cell in each bit cell string is written at a position off-track by 1/2 track in the cross-track direction, and takes a different value for every track width in the cross-track direction. (c) The remaining bit cell strings other than the one bit cell described in paragraph (b) are written on the track center and identify each data track that is a member of a set of adjacent data tracks. Construct a code string,
Only one bit cell between mutually adjacent bit cell rows takes a different value.