JPH03104067A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To obtain a stable sector servo system even when there is a servo signal for obtaining sector information, servo signal for coarse control for obtaining track information and servo signal for fine control for obtaining position error information. CONSTITUTION:In the magnetic disk device of the sector servo system, the servo information composed of the respective servo signals in servo areas shown in a figure are recorded. Thus, concerning the servo signal for coarse control, since plural gray codes showing the same track address are made continuous, the correct track address can be read by a majority principle even when a code is erroneously reproduced by the defect of the medium. Concerning the servo signal for fine control, since it is formed by plural die bit patterns alternatively deviated in half track pitch outer circumference and inner circumference sides, even the comparatively short medium defect or modulation error can be prevented as well.

Description

[Detailed description of the invention]

[Industrial field of application] Concerning servo information for magnetic disk drives using the sector servo method. [Prior Art] The sector servo system is already generally known as shown in U.S. Pat. No. 3,185,972, and the positioning information is also in the burst format shown in the above patent, or in the die format shown in U.S. Pat. No. 3,534,344. There are various types such as chinoya called bit pattern and chinoya called tribit pattern shown in US Pat. No. 3,691,543. Since these patterns are generally used during track following control, they are called fine adjustment servo information. Seek system {During wholesale, coarse adjustment servos and fine signals containing track address information are used to detect the head position. The sex servo system including the above two servo signals is disclosed in US Pat. No. 4,032,984, US Pat.
There are various publications such as No. 79256 and No. 4424543. The track address mentioned above is based on the above-mentioned U.S. Patent No. 403.
As shown in No. 2984, it is generally displayed in gray code. Gray code is a series of 6 values that differ by only 1 bit between adjacent codes, 1960
McGraw-11i 1 1 published by ``Digi''
talComputer and ControlE
ngineering" P517, and is already a common code. There are also various ways to express each bit value of the Gray code, such as those that apply the dibit pattern and tribit pattern mentioned above. [Problems to be Solved by the Invention] In the conventional example described above, countermeasures against servo information reproduction errors caused by medium defects, electrical noise, vibration shock, motor rotation fluctuation, etc. are insufficient. With this method, the sampling period cannot be high, so the control band cannot be widened. Therefore, rapid fluctuations in servo information due to reproduction errors can cause a significant deterioration of control stability, so it is difficult to obtain servo information accurately. This is very important. The purpose of the present invention is to prevent errors in reproducing servo information due to medium defects, etc., as described above, and to provide a servo signal that allows accurate servo information to be obtained. Means 1 In the magnetic disk device of the present invention, in the servo information recorded on the magnetic disk of a sector servo type magnetic disk device consisting of a plurality of sectors, the servo information is B. A servo signal for coarse adjustment to obtain rack information; and c. A servo signal for fine adjustment to obtain position error information. The above servo signal: a. Detects the beginning of the servo information area. b. A synchronization signal area for synchronizing the servo signal for obtaining the sector information and the coarse adjustment servo signal for obtaining the track signal; c. From the plurality of sectors. a sector mark signal area that indicates the sector position and constitutes a servo signal for obtaining the sector information; d. indicates the type of signal indicated for the sector and constitutes a coarse adjustment servo signal for obtaining the sector information; a signal area classified by sector; e. a rough adjustment servo signal area indicating an approximate relative position or absolute position with respect to the track and forming a coarse control servo signal for obtaining the track information; f. accurate relative position with respect to the track; A fine adjustment servo signal area for indicating the position and obtaining the position error information, and a fine adjustment servo signal area for holding the fine adjustment servo signal. A hold time area for providing time may be added.Furthermore, the coarse adjustment servo signal is formed by a plurality of consecutive gray codes indicating the same track address. Furthermore, the coarse adjustment servo signal is formed of a gray code indicating a track address, and furthermore, the @minimum code is formed of a plurality of consecutive identical bits.

[For use]

Due to the configuration of each servo signal in the servo information area above, for the coarse adjustment servo signal, multiple gray codes indicating the same track address are consecutive, so a certain code may be erroneously reproduced due to a media defect, etc. Even if the track address is correct, it is possible to read the correct track address based on the principle of majority voting. Furthermore, the fine adjustment servo signal is formed from a plurality of dibit patterns that are alternately shifted toward the outer circumference and the inner circumference by half a track pitch, and the position error signal is formed by the positive pulse signal waveform and negative pulse signal waveform of the dibit pattern. Since the value is valid only when the integral values of both pulse waveforms are equal, it is possible to avoid bit errors due to relatively short media defects, and it is possible to avoid bit errors due to relatively short media defects. By taking , it is possible to avoid modulation errors caused by relatively long media defects, and it is possible to accurately reproduce the position error signal. Therefore, even if a medium defect or electrical noise occurs, it is possible to accurately reproduce track addresses and position error signals, so stable control can be achieved during seek control and track following control, making it possible to use the sector servo method. performance as a magnetic disk device. [Examples] Examples of the present invention will be described in detail below based on the drawings. FIG. 7 is a diagram showing the configuration of the servo area and data area of a magnetic disk in a general sector servo system. In the sector servo method, a servo area is placed in each sector. Figure 8 is a diagram showing the configuration of each signal area between sectors. Normally, the servo area is placed at the beginning of the sector, and a speed buffer is provided at the rear end for absorbing fluctuations in signal length due to fluctuations in rotation of the motor that rotates the magnetic disk. Figure 1 is a signal configuration diagram of the servo area of this embodiment.
First, a servo start signal area 1l is arranged to clearly indicate that it is a servo sector. Usually formed in a DC-extinguished region. Next, a synchronization signal area l2 for synchronizing the signals up to the coarse adjustment servo area 15 is arranged. It is usually formed by a signal with a constant frequency. Next, a sector mark signal area l3 for servo sector recognition is arranged. Furthermore, a large sector signal area 14 for broadly classifying sector types is arranged. Here, signals that can be classified as index sectors or normal sectors, as well as sectors in the outer guard band area or data sectors are recorded. Next, a rough adjustment servo signal area l5 is arranged in which a track address and the like for head position detection during seek control are written. Details will be described later. Next, a fine adjustment servo signal area 16 is arranged to detect a position error signal during track following control. The details will be described later, but the above two servo signal areas for coarse adjustment and fine adjustment are very important areas. Finally, if necessary, a hold time region 17 is arranged to completely hold the fine adjustment servo signal. Now, regarding the coarse adjustment servo area, as explained in the conventional example, the track address is usually expressed by a gray code. Figure 2 is a horizontal cell diagram representing each bit value of the Gray code. The tri-bit cell structure is such that the bit value φ, 1 is determined based on the magnetization reversal position on the left or right side of the center of the cell. In the dibit format, bit values are determined based on the presence or absence of a dibit pattern within a cell. Also, 6! In the + direction format, the bit value is determined depending on whether the 6n inversion pulse in the cell is a positive pulse or a negative pulse. Figure 3 shows the binary code 1 according to each cell format in Figure 2.
FIG. 2 is an explanatory diagram showing a 6n pattern and an output waveform when expressing 01001. Figure 3(a) is a tribit format,
FIG. 3(b) shows the dibit format, and FIG. 3(c) shows the magnetization direction format. In the present invention, in the coarse adjustment servo area, there are a plurality of consecutive gray codes indicating the same track address of various expressions as described above. Therefore, even if a code error occurs in one of the codes due to a media defect, as long as the other codes are correctly reproduced, it is possible to read the correct track address based on the principle of majority voting. Next, regarding the servo area for fine adjustment, as explained in the conventional example, various signals are already used for patterns that produce position error signals during track following control. In this embodiment, a dibit pattern is used, and is composed of a plurality of dibit patterns that are alternately shifted between a half-track pitch outer circumference example and an inner circumference example. Figure 4 is a diagram of the fine adjustment servo pattern of this embodiment using a dibit pattern. The output waveforms reproduced by head a located at the center of track n and head b located slightly shifted toward track n+1 are shown below. There is. As shown by the output of head b, if the head deviates from the track center, the outputs of the alternating dive bit backs become unbalanced. Normally, the difference in these outputs is detected as the amount of positional error, but in this embodiment, the difference between the integrated values of the positive and negative pulse waveforms of the alternating dibit pattern is detected as the amount of positional error. FIG. 5 is an output waveform diagram of two alternating dibit patterns. The first dibit pattern is divided into a first output waveform region 2l of a negative pulse waveform and a second output waveform region 22 of a positive pulse waveform, and the respective waveform integral values are k, . k. Suppose that The next dibit pattern is similarly divided into a third output waveform region 23 and a fourth output waveform region 24, and the respective waveform integral values are calculated as kx. Let it be k4. The positional error amount is detected from the difference between kl +lc and ks+kn, and in this embodiment, since a plurality of positions are connected in succession, the influence of modulation errors can be avoided by taking their average value. Also, in principle k1
=k. ．． k. =k. Therefore, due to bit errors caused by relatively short media defects, k. ≠k,, k2≠k4
In this case, the influence of bit errors can be avoided by not using these integral values for position error detection6.Therefore, with the servo signal configuration of this embodiment, it is possible to obtain accurate servo information. be. FIG. 6 is a diagram of another example fine adjustment servo pattern using a tri-bit pattern. The output waveforms are shown shifted by half a track pitch with respect to the track center line, and the output waveforms reproduced by head a located at the center of track n and head b located slightly shifted toward track n+1 are also shown. There is. When the head deviates from the track center, the magnetization reversal outputs of the same polarity at two alternately deviated positions become unbalanced. Normally, the difference in these outputs is detected as a position error, but since these two must be separated at high speed, detection errors are likely to occur and reliability is lacking. However, in a tri-bit pattern, pulses (clock pulses) of the same polarity always occur at equal intervals, so if the output difference is detected while synchronizing using these pulses, reliability will be improved. [Effects of the Invention] As described above, according to the present invention, coarse adjustment servo information such as track addresses, which are important during seek control, and position error signals, which are important during track following control, can be detected in a sector servo type magnetic disk device. The servo information for fine adjustment can be obtained accurately even when medium defects or electrical noise occur, making it possible to perform stable control during seek control or track following control.
This has the effect of ensuring sufficient performance as a disk drive.

[Brief explanation of drawings]

FIG. 1 is a signal configuration diagram of the servo area of this embodiment. Figure 2 is a cell structure diagram representing each bit value of the Gray code. Figure 3 shows the binary code 101 for each cell format in Figure 2.
It is an explanatory diagram showing a Cnization pattern and an output waveform when expressing 001. FIG. 4 is a diagram of a fine adjustment servo pattern of this embodiment using a dibit pattern. FIG. 5 is an output waveform diagram of two alternating dibit patterns. FIG. 6 is a fine adjustment servo pattern diagram of another embodiment using a tri-bit pattern. FIG. 7 is a diagram showing the configuration of the servo area and data area of a magnetic disk in a general sector servo system. Figure 8 is a diagram showing the configuration of each signal area between sectors. 2 3 l1 l2 l 3 l 4 l 5 l 6 l 7 2l 22 23 2 4 Servo area data area Servo start signal area Synchronization signal area Sector mark signal area Sector major signal area Servo area for coarse adjustment Servo area for fine adjustment Servo area hold time area 1st output waveform area 2nd output waveform area 3rd output waveform area 4th output waveform area Figure 4 Figure 5 Figure 8 Figure 7

Claims (1)

[Claims] 1) In servo information recorded on a magnetic disk of a sector servo type magnetic disk device consisting of a plurality of sectors, the servo information includes: A, a servo signal for obtaining sector information, and B. C. A servo signal for coarse adjustment to obtain track information, and C. A servo signal for fine adjustment to obtain position error information. (b) a synchronization signal area for synchronizing the servo signal for obtaining the sector information and the coarse adjustment servo signal for obtaining the track information; (c) indicating the sector position from the plurality of sectors; a sector mark signal area that constitutes a servo signal for obtaining the sector information; and d) a sector-based signal area that indicates the type of signal shown in the sector and that constitutes a coarse adjustment servo signal for obtaining the sector information. , e, a rough adjustment servo signal area that indicates an approximate relative position or absolute position with respect to the track and constitutes a coarse adjustment servo signal for obtaining the track information; A magnetic disk device comprising: a servo signal area for fine adjustment for obtaining error information; 2) A magnetic disk drive characterized in that a hold time area for providing time for holding the fine adjustment servo signal is added after the fine adjustment servo signal area according to claim 1. 3) A magnetic disk device, wherein the coarse adjustment servo signal according to claim 1 is formed of a plurality of consecutive gray codes indicating the same track address. 4) A magnetic disk device according to claim 1, wherein the coarse adjustment servo signal is formed of a gray code indicating a track address, and each minimum code is formed of a plurality of consecutive identical bits. 5) A magnetic disk device, wherein each bit value of the Gray code according to claim 3 or 4 is expressed as a tri-bit format signal, a di-bit format signal, or a magnetization reversal direction. 6) A magnetic disk drive in which the fine adjustment servo signal according to claim 1 is comprised of a plurality of dibit patterns alternately shifted toward the outer circumference and the inner circumference by half a track pitch. 7) When forming a position error signal from the fine adjustment servo signal according to claim 6, an integral value of the positive pulse signal waveform and a negative pulse signal waveform of the dibit pattern is used, and further, an integral value of both pulse signal waveforms is used. A magnetic disk device characterized in that it is effective only when the values are equal. 8) A magnetic disk drive in which the fine adjustment servo signal according to claim 1 is comprised of a plurality of tri-bit patterns alternately shifted toward the outer circumference and the inner circumference by half a track pitch. 9) A magnetic disk drive characterized in that a speed buffer area is provided at the end of each sector containing the servo information according to claim 1, for absorbing rotational fluctuations of a motor that rotates the magnetic disk.