JPH0464912A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To always perform the on-track control by detecting the magnitude between the positive peak and the negative peak of a dibit and performing the track follower control based on this magnitude. CONSTITUTION:Gate signals 6 to 9 of peak holding circuits 14 to 17 which detect the negative peaks of respective position information are synchronous with negative peak appearance points of position information A to D. At the time of seek operation, a position signal 38 obtained from positive peaks of position information A and C and a position signal 39 obtained from those of position information B and D are differentiated to generate a speed signal, and the speed control is performed. At the track follow operation, position signals (App-Dpp) 40 and (Bpp-Dpp) 41 obtained by peak-to-peak amplitudes of position information which are not affected by magnetization interference are used to perform the position control because the precise operation is required, and the track follow operation is so performed that these position signals 40 and 41 are 0.

Description

TECHNICAL FIELD The present invention relates to a magnetic disk device, and more particularly to a magnetic disk device that performs head positioning control by reading position information of a dibit pattern written in advance on a servo surface of a magnetic disk. .

2. Description of the Prior Art A conventional head positioning system for this type of magnetic disk drive is implemented using a configuration as shown in FIG. HDA49
A certain surface of the disk stack 45 inside is used as a servo surface 46, and this servo surface 46 has, for example, two
Position information of the phase dive pattern is written.

This position information is read out by a read-only servo head 44 and inputted as a two-phase dibit pattern signal 1 to a position signal demodulation circuit 42. This position signal demodulation circuit 4
2, the position signal 50 of the head 43 is demodulated from the two-phase dive pattern signal using the gate signal 47 for sample and hold.

During a seek operation (ie, the current position of the head) - During a seek operation from the rack position to the target track position, seek servo is performed by speed control. Therefore, the position signal 50
is input to the electronic tachometer 58 and differentiated, and then becomes a speed signal 59 and input to the speed error signal generation circuit 65.

In this speed error generation circuit 65, a difference between the speed signal 59 and the speed reference signal 64 is generated so as to follow the speed reference signal 64 of a predetermined profile, and the difference signal is used as the speed error signal 66 in the mode. The signal is supplied to the switching circuit 67.

In the mode switching circuit 67, the speed error signal 66 is selected during the seek operation, and this becomes the drive signal 68 and is inputted to the power amplifier 69. After the current is amplified by the power amplifier 69, it is input as a drive current 70 to the voice coil type head drive device 48, where a seek operation is performed.

The speed reference signal 64 is obtained by sequentially reading profile data written in the ROM 61 in accordance with the address (signal indicating the number of remaining tracks) 60 (62), and converts it into an analog signal using the DA converter 63. This is a signal converted into data.

Position control is performed during a track following operation to maintain the head 43 on the target track position.

Therefore, the position signal 50 is input to the slope select circuit 52, and the slope of the position signal 50 is selected by the slope select signal 5 corresponding to the track position to be positioned.

The integration circuit 54 integrates the selected position signal 53, and controls the proportional element and the integral element of the PID control (proportional element, integral element, differential element) in position control.

This output integral position signal 55 is input to a position signal summing amplifier 56, to which a speed signal 59 indicating a differential element of PID control is added, and is supplied as a position error signal 57 to a mode switching circuit 67.

The mode switching circuit 67 selects the position error signal 57 during the track follow operation, and controls the drive device 48 via the power amplifier 69 as in the seek operation.

FIG. 4(a) shows a positional information pattern written on the servo surface, and FIG. 4(b) shows an example of the waveform of a two-phase digit pattern signal read out by the servo head.

The two-phase dibit pattern signal is composed of dibit position information A to D at four locations indicating position information, and during track follow operation, the amplitude of each positive pix of position information A and C1 or B and D is changed depending on the track. Position control is performed so that they are equal.

Therefore, the conventional position signal demodulation circuit 42 has a configuration shown in FIG. The two-phase dip pattern signal 1 from the servo head is simultaneously input to four peak hold circuits 10 to 13, and the gate signal 2 of each circuit 10 to 13 is
5 has a timing for peak-holding the positive peaks Ap-Dp of the position information A-D of the four dibits.

Hold outputs Ap and c of peak hold circuits 10 and 12
A differential amplifier 26 that detects the difference between the peak hold circuits 11 and 13 and a differential amplifier 27 that detects the difference between the hold outputs Bp and Dp of the peak hold circuits 11 and 13 are provided.

The respective outputs 38 and 39 of the differential amplifiers 26 and 27 are position signals from which sampling noise of the difference signal has been removed by an internal low-pass filter.

With the miniaturization and increase in capacity of magnetic disk drives, the bit density per area of positional information written in advance on the servo surface has increased, and therefore, due to magnetization interference between magnetization patterns, As shown in FIG. 5, the positive peak value of the position information C may decrease and the negative peak value may increase.

When the servo head is positioned directly above the track, the amplitudes of position information A and C should originally be the same, and the servo operation is performed so that they are the same, but in reality, the amplitudes of position information A and C should be the same. becomes smaller than the positive amplitude of the positional information A due to magnetization interference of the adjacent positional information B.

For this purpose, when the position signal demodulation circuit 42 demodulates the position signal 38 (see FIG. 3) and performs head positioning operation, the servo operation is performed so that the positive pix amplitudes of position information A and C are equal. It has the disadvantage of being off-track.

OBJECTS OF THE INVENTION An object of the present invention is to provide a magnetic disk device that is capable of normal on-track control even if the repeak amplitude changes due to mutual magnetization interference of position information.

Structure of the Invention According to the present invention, position information of a dibit pattern written on the servo surface of a magnetic disk is read out, and track follow is performed using a dibit corresponding to a predetermined location of this dibit pattern signal. A magnetic disk device configured to perform control based on means for detecting the magnitude between the positive peak and the negative peak of the dibit, and the magnitude between the detected iF-peak and the negative peak. A magnetic disk device characterized by including means for performing track follower control? 11.

Principle of the Invention The peak change due to magnetization interference of position information is as shown in the waveform of position information C in Figure 5, as the positive peak decreases, the negative peak increases by that amount, and as a result, the position information C The fact is that the peak-to-peak amplitude Cpp of is equal to and identical to Cpl in the absence of magnetization interference.

Therefore, in the present invention, based on this fact, instead of comparing the positive peak values of the position information, the peak-to-peak amplitudes of the position information A11), Cpll, B I
II) Comparison control is attempted using Dpp.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, which is a specific embodiment of a position signal demodulation circuit 42, and parts equivalent to those in FIG. 3 are designated by the same reference numerals.

In this example, the conventional circuit shown in FIG.
Each positive peak value Ap-Dp of D is detected and a position signal (Ap
-Cp) and (Bp -Dp), there are also peak hold circuits 14 to 17 that detect each negative peak value Ap- to Dp- of position information, and peak-to-peak peak-to-peak circuits of each position information A-D. Differential amplifier 2 that obtains amplitudes App to Dpp
8 to 31, position signals (A pp-Cpp) and (B
differential amplifiers 36 and 37 for obtaining pp-D pp) are added.

The gate signals 6 to 9 of the peak hold circuits 14 to 17, which respectively detect negative peaks of each position information, are signals synchronized with the negative peak appearance points of each position information A to D shown in FIG. 4(B).

During a seek operation, as in the conventional example, a velocity signal is generated by differentiating the position signal 38 obtained from the positive peaks of position information A and C and the position signal 39 obtained from the positive peaks of B and D. and perform speed control.

During track following operation, since precision movement is required, the position signal (App-Dp
Position control is performed using p) 40 and (Bpp-Dpp) 41, and a track follow operation is performed so that these position signals 40°41 become zero.

It is assumed that, like the differential amplifiers 26 and 27, the differential amplifiers 36 and 37 have internal low-pass filters and have a function of removing sampling noise.

Effects of the Invention As described above, according to the present invention, a position signal is generated using the peak-to-pix value difference between positive and negative position information of a dibit pattern signal, and the peak-to-peak value of this position information is Since it is not affected by magnetization interference and is constant, it has the effect that on-track control is always possible.

[Brief explanation of drawings]

Fig. 1 is a circuit block diagram of an embodiment of the present invention, Fig. 2 is a circuit block diagram of a servo control system of a magnetic disk device, and Fig. 3 is a circuit block diagram of an embodiment of the present invention.
The figure shows an example of a conventional position signal demodulation circuit.
) is a diagram showing the positional information pattern written on the servo surface, FIG. The figure is a diagram showing the waveform of a two-phase Daipitz I pattern signal in the case of magnetization interference. Explanation of symbols of main parts 10 to 17...Peak hold circuits 26 to 31
゜3637... Differential amplifier circuit 43... Data head 44... Servo head 46... Servo surface

Claims (1)

[Claims] (1) A magnetic system that reads the position information of a dibit pattern written in advance on the servo surface of a magnetic disk and performs track follow control using dibits corresponding to predetermined locations of this dibit pattern signal. A disk device comprising means for detecting the magnitude between the positive peak and negative peak of the dibit, and means for performing track follower control based on the magnitude between the detected positive peak and negative peak. A magnetic disk device comprising: