JPH0714329A - Disk storage device - Google Patents

Abstract

PURPOSE:To improve control performance for positioning a head such as improvement of precision for positioning a head, shortening of moving time of a head and the like by reducing a noise of demodulated frequency components included in a position error signal. CONSTITUTION:After a servo signal read out from four servo information patterns in a servo signal 53 read out from a head 1 and amplitude-controlled in peak-held by a peak-hold circuit 50, difference signals POSA, POSB are generated by a differential amplifier 56. After that, a notch filter 11 reducing demodulated frequency components is provided, and signals obtained by passing difference signals POSA, POSB through the notch filter 11 are mode to be position error signals PESA, PESB.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk storage device, and more particularly to a disk storage device for improving the position detection accuracy by reducing the noise of the demodulation frequency contained in the position error signal which is the output signal of the demodulation circuit. .

[0002]

2. Description of the Related Art Conventionally, a disk storage device detects a change in magnetization of N / S poles or a pit as servo information recorded in advance on a disk surface so that a head comes to a track center line of a data disk. In addition, track tracking control is performed.

The N / S poles or pits serving as servo information are arranged at offset positions on both sides of the track center line. This servo information is recorded on the track at regular intervals. Therefore, when the disk is rotating, the servo information is read out from the head as a servo signal at a constant cycle. When the head is on the track center line, the amplitude or time integrated value of the servo signal read from the two servo information located on both sides of the track center line becomes equal, but when the head deviates from the track center,
One of the amplitudes or time integrated values of the two read servo signals is larger and the other is smaller than when the head is located at the center of the track. Therefore, the demodulation circuit outputs the difference between the amplitude or the time integral value of the servo signal read from the two servo information as a position error signal.
However, one of the above-mentioned conventional demodulation circuits, since the servo signal read from the two servo information is sampled only at a certain time interval, the read servo signal is peak-held at a constant timing, and further, A differential signal is generated by the differential amplifier and output as a position error signal. Another conventional technique is to integrate the read servo signal at a fixed timing and to generate a difference signal with a differential amplifier to output a position error signal as disclosed in JP-A-64-35787. There is.

[0004]

Since the position error signal changes stepwise at every read cycle of the signal read from the servo information, the position error signal has a read frequency and an integer multiple thereof. Frequency noise is superimposed. As a method of reducing the influence of this noise, a low-pass filter that leaves only the frequency component necessary for positioning and cuts the high frequency component has been used conventionally. However, with the recent increase in capacity of disk devices, track intervals have become narrower, and there is a demand for improvement in head positioning accuracy. Further, the change in the position error signal when the head moves at high speed is rapid. Therefore, the signal band required for the position error signal is approaching the reading frequency which is a noise component included in the position error signal, and it is also required to increase the band of the position error signal. In a recent disk storage device, if an attempt is made to secure a sufficient frequency band of the position error signal, the cutoff frequency of the low-pass filter for removing noise is set high, so that sufficient noise cannot be removed. Therefore, there is a problem that the servo system for moving and positioning the head is greatly affected.

[0005]

In order to achieve the above object, the demodulation circuit of the disk storage device of the present invention has a notch for removing the read frequency component of the servo signal, or the read frequency and its harmonic components. Achieved by providing a filter and passing the difference signal between the peak hold signals of the two servo signals or the difference signal of the integrated signals of the two servo signals through this notch filter as the position error signal. To be done.

[0006]

The removal method using the conventional low-pass filter can remove a wide range of frequency components above the cut-off frequency of the low-pass filter, but when the signal band required for the position error signal and the noise of the reading frequency of the servo information are close to each other,
Sufficient noise reduction cannot be achieved. However, since the demodulation circuit of the disk storage device according to the present invention can remove the noise of the servo information reading frequency by the notch filter, the demodulation circuit noise can be removed while maintaining the signal band required for the position error signal.

[0007]

【Example】

(First Embodiment) An embodiment of the present invention according to claim 1 in a magnetic disk device will be described below with reference to the drawings. First,
First, the conventional method will be described with reference to FIGS.

FIG. 2 is a block diagram of a head positioning control system of the magnetic disk device. In the control system of FIG. 2, servo information 3 read from the head 1 facing the disk 2
The demodulation circuit 4 converts the position error signal 5 into a position error signal 5, the positioning controller 6 performs a compensation calculation so as to make the position error signal 5 zero, and outputs a positioning compensation signal 7. The power amplifier 8 sends a current proportional to the positioning compensation signal 7 to the voice coil motor (VCM) 9, and the VCM 9
A force proportional to the current is generated to drive the carriage 10 having the head 1 mounted thereon, and the head 1 is moved and positioned.

As shown in FIG. 3, the demodulation circuit 4 outputs two kinds of position error signals PESA and PESB proportional to the deviation from the track center on the head 1 and the disk 2. PESA and PESB are signals with a 90-degree phase difference, and PESA becomes zero at the center of an even track.
B is a signal that becomes zero at the center of the odd track. The positioning controller 6 determines the PES according to the target track.
The compensation calculation is performed using any of A, PESB, -PESA, and -PESB.

Next, a method of generating the position error signals PESA and PESB will be described with reference to FIGS. 4 and 5.

FIG. 4 is a diagram showing a pattern of servo information on the disk and a signal waveform in the demodulation circuit, and FIG.
It is a figure which shows the structure of the demodulation circuit 4 of a conventional system.

FIG. 4A shows the relationship between the magnetization pattern of servo information and the magnetic head 1. The servo pattern of FIG. 4 is a pattern called a two-phase servo pattern, and includes a sync pattern 43 for generating a clock signal required for synchronization in the demodulation circuit and four servo information patterns for generating a position error signal. 44, 45, 4
6,47 are recorded as a set. The sync pattern 43 and the servo information pattern 4 are arranged in the disk circumferential direction.
A set of 4, 45, 46, 47 is repeatedly recorded. Each servo information pattern is a pattern having a width of two data tracks, and is recorded every two data tracks. Further, different types of servo information patterns are recorded while being shifted every other data track. In the demodulation circuit 4, the signal read from the head 1 is amplified by the preamplifier 51 and further amplitude controlled by the AGC amplifier 52 to generate the servo signal SRVSIG53.
The AGC amplifier 52 adjusts the gain by the AGC control signal 54 and keeps the amplitude fluctuation of the read voltage caused by the fluctuation of the distance between the disk 2 and the head 1 constant. FIG. 4B shows a servo signal whose amplitude is controlled by the AGC amplifier.
This is the waveform of SRVSIG53. Since the servo pattern of FIG. 4A is repeatedly recorded, the servo signal SRVSIG of FIG. 4B also has a repetitive waveform. The center of the data track is the servo information pattern 44 and the servo information pattern 46.
Of the servo information pattern 45 or the servo information pattern 47. FIG. 4A shows a state where the head 1 is located on the boundary line between the servo information pattern 44 and the servo information pattern 46. At this time, the read servo signal is shown in FIG. Since the peak voltage 48 of the signal reproduced from the servo information pattern 44 and the peak voltage 49 read from the servo information pattern 46 are equal, it can be seen that they are positioned at the track center. In the demodulation circuit 4, in order to detect this peak voltage, a clock generation circuit (not shown) generates the clock signals CLK1 to CLK4 shown in FIG. 4C, and only when the clock signal CLK1 is high, The peak hold circuit 50a detects the peak, and when it is low, the peak voltage is held. Similarly, the peak hold circuits 50b to 50d perform peak detection only when the clock signals CLK2 to CLK4 are high, and hold the peak voltage when they are low. The output signals of the peak hold circuits 50a-50d are shown in FIG. 4 (d). Four peak hold circuit outputs P _{1 to} P
₄ is given to the adder circuit 55 and the differential amplifiers 56a and 56b. The adder circuit 55 sends the AGC control signal 54 to the AGC amplifier 52 to control the gain of the AGC amplifier 52. The differential amplifier 56a produces a POSA signal from the difference between the peak hold circuit outputs P ₂ and P ₄ , and the differential amplifier 56b produces P OS from the difference between the peak hold circuit outputs P ₁ and P _3.
Creating the OSB signal. Further, high-frequency components are removed by the low-pass filters 57a and 57b to generate the position error signals PESA and PESB. As a result, the position error signals PESA, PE as shown in FIG.
I'm getting SB.

However, as described above, the output value of the peak hold circuit changes stepwise in the peak detection state. This is because peak detection is performed at regular time intervals, the head position moves within that time interval, and the charge stored in the capacitor in the peak hold circuit is discharged to lower the voltage. Can be mentioned. In this way, the noise of the demodulation frequency superimposed on the output signals of the peak hold circuits 50a to 50d is superimposed, and as a result, the demodulation frequency noise is also superimposed on the position error signals PESA and PESB, and the performance of the head positioning control system is improved. Is a factor that deteriorates.

Therefore, in the disk storage device of the present invention,
The demodulation circuit shown in FIG. 5 is used instead of the demodulation circuit shown in FIG. 5 to reduce the demodulation circuit noise. As described above, the difference signals POSA, POSB of the output signals of the peak hold circuit
The noise of the demodulation frequency is superimposed on. So POS
The position error signals PESA and PESB are obtained by passing the demodulation frequency components included in A and POSB through the notch filters 11a and 11b.

The frequency characteristics of the notch filters 11a and 11b are shown in FIG. The notch filters 11a and 11b are inserted for the purpose of reducing demodulation frequency noise. Since the actual difference signal contains not only the demodulation frequency f _d (Hz) but also its harmonic components n · f _d (Hz) (n = 2, 3, ...), connect notch filters in multiple stages. , N · f _d (Hz)
It is also possible to further reduce demodulation noise by inserting a notch filter having a frequency characteristic as shown in FIG. 7 for removing (n = 1, 2, ...).

As described above, it is possible to obtain a position error signal in which the demodulation frequency noise is reduced and the S / N is good and the band is high, and the head positioning control can be performed at high speed and with high accuracy.

(Second Embodiment) An embodiment of the present invention according to claim 2 in an optical disk device will be described below with reference to the drawings. The structure of the head positioning control system of the optical disk is basically the same as that of the control system of FIG. 2 shown in the first embodiment, except that the head 1 is not a sensor for catching magnetism but a light for catching light. It is a sensor head, and the form of the servo information is a hole called a pit instead of the magnetization signals of the N and S poles of the magnetic disk device. FIG. 8 shows a pit pattern which is servo information used in the optical disk device and a signal waveform of the demodulation circuit. As shown in FIG. 8A, the pits serving as servo information are pits P _A and P _B arranged at offset positions on both sides of the track center line. The servo signal SRVSIG is obtained by receiving the light spot 80 from the head 1 and converting the reflected light amount into an electric signal. FIG. 8 shows a state in which the head 1 is positioned at the track center. As shown in FIG. 8B, when the head 1 is positioned at the track center, it is read from the pit P _A. The time integrated value of the read servo signal and the time integrated value of the servo signal read from the pit P _B become equal. When the head 1 deviates from the track center, one time integral value of the read servo signal becomes large and the other becomes small. Therefore, in order to compare the time integrated values of the two servo signals, the clock signal CLK5 (FIG. 8 (c)) generated by the clock generation circuit (not shown) and the servo signal SRVS are generated.
IG is multiplied in the multiplication circuit 91 to obtain the signal S1 shown in FIG. That is, in S1, the servo signal corresponding to the pit P _A has the same polarity, and the servo signal corresponding to the pit P _B is inverted. If the time integration value of the plus part and the time integration value of the minus part of the signal S1 are equal, it means that the signal S1 is positioned at the track center. Further, when the signal S1 is integrated by the integration circuit 92 while the clock signal CLK6 (FIG. 8 (e)) generated by the clock generation circuit (not shown) is high, the position shown in FIG. 8 (f) is obtained. The error signal PES can be obtained.

As shown in FIG. 8 (f), the position error signal P
The ES reproduces an accurate position error signal when the integration operation is completed, but deviates from an accurate value during the integration operation. Since this shift occurs at every demodulation cycle, noise at the demodulation frequency is superimposed on the position error signal PES. This noise is a factor that deteriorates the performance of the head positioning control system.

Therefore, in the disk storage device of the present invention,
Instead of the demodulation circuit of FIG. 9, the demodulation circuit of FIG. 10 is used to reduce the demodulation circuit noise. As described above, the demodulation frequency noise is superimposed on the output signal S2 of the integrating circuit 92. Therefore, the demodulation frequency component contained in S2 is passed through the notch filter 11 to obtain the position error signal PES.

The frequency characteristic of the notch filter 11 is shown in FIG.
Alternatively, it is the same as that shown in FIG. This notch filter has demodulation frequency noise or demodulation frequency f
_d (Hz) and its harmonic component n · f _d (Hz) (n = 2
, 3) can be removed to reduce demodulation noise.

In this way, it is possible to obtain a position error signal in a high band having a good S / N with reduced demodulation frequency noise, and it is possible to perform head positioning control with high speed and high accuracy.

[0022]

According to the present invention, the demodulation frequency noise included in the output signal of the demodulation circuit can be reduced and a position error signal having a good S / N and a high band can be obtained. As a result, the performance of the head positioning control system can be improved, and the head moving time and the head positioning accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a demodulation circuit of a magnetic disk device to which the present invention is applied.

FIG. 2 is a block diagram of a head positioning control system of a disk storage device.

FIG. 3 is an explanatory diagram of a position error signal.

FIG. 4 is an explanatory diagram of a servo information pattern of a magnetic disk device and a signal waveform of a demodulation circuit.

FIG. 5 is a block diagram of a demodulation circuit of a conventional magnetic disk device.

FIG. 6 is a frequency characteristic diagram of a notch filter that reduces a demodulation frequency.

FIG. 7 is a frequency characteristic diagram of a notch filter that reduces a demodulation frequency and its harmonics.

FIG. 8 is an explanatory diagram of a servo information pattern of an optical disk device and a signal waveform of a demodulation circuit.

FIG. 9 is a block diagram of a demodulation circuit of an optical disc device according to a conventional technique.

FIG. 10 is a block diagram of a demodulation circuit of an optical disc device according to the present invention.

[Explanation of symbols]

1 ... Head, 11 ... Notch filter, 50 ... Peak hold circuit, 51 ... Preamplifier, 52 ... AGC amplifier, 5
3 ... Servo signal SRVSIG, 56 ... Differential amplifier.

Claims (2)

[Claims] 1. A disk in which servo information recorded at offset positions on both sides of a center line of the track to determine the positions of a plurality of tracks is repeatedly recorded in a circumferential position of the disk, and the servo information is read. Then, the head for converting into a servo signal, the amplitude of the servo signal read from the servo information recorded at the offset position on one side of the track, and the servo information read from the servo information recorded at the offset position on the other side of the track A demodulation circuit that outputs a difference signal of the amplitude of the servo signal as a position error signal corresponding to a position error between the head and the track, and control means that moves and positions the head on the track based on the position error signal. In the disk storage device having, the demodulation circuit reads the servo information from the difference signal at a frequency. A disk storage having a notch filter for removing a component or a read frequency component and its harmonic component, and a signal obtained by passing the difference signal through the notch filter is used as the position error signal. apparatus. 2. A disk in which servo information recorded at offset positions on both sides of a center line of the track is repeatedly recorded in a disk circumferential direction to determine the positions of a plurality of tracks, and the servo information is read. Then, a head for converting into a servo signal, a time integrated value of the servo signal read from the servo information recorded at the offset position on one side of the track, and servo information recorded at the offset position on the other side of the track And a demodulation circuit for outputting a difference signal of the time integrated value of the servo signal read from the head as a position error signal corresponding to a position error between the head and the track, and moving the head onto the track based on the position error signal to perform positioning. In the disk storage device having a control means for controlling the servo information, the demodulation circuit reads the servo information from the difference signal. A notch filter for removing a read frequency component or a read frequency component and its harmonic component, and a signal obtained by passing the difference signal through the notch filter is used as the position error signal. Disk storage device.