JP2746148B2 - Position error correction method for magnetic disk drive using MR head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position error correction method for a magnetic disk drive for reading servo information using an MR head.

[0002]

2. Description of the Related Art In a magnetic disk device generally used at present, a magnetic head position is defined as a position error signal generated based on a servo signal obtained from a disk surface by a magnetic head (hereinafter referred to as "head"). can get. Hereinafter, the relative position between the disk surface and the head is referred to as a head position.

The head positioning control system controls the head position based on the position error signal.

For this reason, if the relationship between the head position and the output of the position error signal changes, the head position is erroneously recognized and directly affects the gain of the control system.

In the conventional magnetic disk drive, since an inductive head is used as a head, a linear region has a sufficient range for head positioning in the relationship between the head position and the position error signal, and the position error signal is automatically gain controlled (AG).
C: Sufficient positioning accuracy including off-track positioning has been obtained by suppressing only amplitude fluctuation by correction at the intersection of automatic gain control and two-phase signals.

[0006]

In a magnetic disk drive, there is a correlation between a head position and a position error signal output, and the head position is obtained from the position error signal based on the correlation.

However, when an MR head is used for reading servo information, it is difficult to use a conventional position error signal correction method because a linear region of the position error signal cannot be sufficiently obtained.

The method of providing a correlation table between the head position and the position error signal in advance has a problem of how many points to take as the correlation data. However, in terms of storage capacity and cost, it is practically very difficult to achieve this.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to avoid the deterioration of head positioning accuracy due to the non-linearity of a position error signal in servo signal detection by an MR head. and, and to provide a position error correcting how the magnetic disk device to correct the position error signal with respect to the head position.

[0010]

In order to achieve the above-mentioned object, the present invention provides one or more magnetic disk media, a composite magnetic head for recording and reproducing data by integrating an inductive head and an MR head, From the servo signal obtained from the disk surface by the MR head,
As a signal having one cycle in two tracks or four tracks,
A position error signal generator for generating a position error signal indicating position error information between the MR head and the center of the data track; converting the position error signal into a digital signal and inputting it to a digital signal processing device; In a magnetic disk drive for generating a control signal of an actuator for moving the head by a processing device, in a step of writing a servo signal on the disk surface, the head position near the center of the data track and detected by a head position detection device In the position error signal generated from the servo signal detected by the MR head, two to several points are detected, and fluctuation rate information approximately obtained as a linear function is written in a storage unit. Before inputting to the digital signal processing device using the fluctuation rate information It was adapted to correct at least gain of the position error information to provide a position error correcting how the magnetic disk device according to claim.

Further, in the position error correcting how the magnetic disk device of the present invention, the position error signal for generating a position error signal indicating a position error information of the data track center and the MR head as a triangular wave signal of the two-phase A magnetic disk device comprising a generator, wherein the digital signal processing device switches the two-phase position error signal and uses the position error signal as position error information, wherein a fluctuation of the head position and the position error signal near the center of the data track. In addition to the rate, the change rate at the position error signal switching point may be written, and the gain of the position error information may be corrected by switching the three change rates.

Further, in the position error correcting how the magnetic disk device of the present invention, preferably, the storage means is characterized by comprising the disk surface.

[0013] In the position error correcting <br/> how the magnetic disk device of the present invention preferably comprises a memory as the storage means, in the step of writing a servo signal on the disk surface, approximately as a linear function The obtained fluctuation rate is written in the memory.

Furthermore, in the position error correcting how the magnetic disk device of the present invention, preferably, in the step of writing a servo signal on the disk surface, to generate a sine wave noise in the digital signal processing apparatus, the head The head is vibrated near the track center by superimposing the sine wave noise on the drive signal of the actuator that moves the actuator, and the magnitude of the position error signal of the same frequency component as the sine wave noise added to the drive signal of the actuator Is configured to be obtained.

[0015]

According to the present invention, it is possible to obtain a more accurate head position by using the corrected position error signal, and to perform head positioning by nonlinearity of the position error signal by detecting a servo signal in the MR head. It is possible to reduce the deterioration of the accuracy and the deterioration of the seek characteristic due to the influence on the head speed obtained by the deviation of the head position and the head position during the seek operation. In the offset seek operation, a desired offset amount can be given to the head.

[0016]

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

[0017]

Embodiment 1 FIGS. 1 and 2 are block diagrams showing the configuration of an embodiment of the present invention. FIG. 1 shows an example of a servo track writer (STW: Servo Track Writer), and FIG. 2 shows a digital signal processor (DSP: Digital).
2 shows an example of a configuration of a servo circuit using a signal processor (Signal Processor).

The magnetic disk drive has one or more magnetic disk media 1 (referred to as a "disk") and a magnetic head 2 for obtaining a servo signal 11 from one or both surfaces thereof.

The magnetic head 2 is a composite magnetic head for recording / reproducing ("head") in which an inductive head for recording signals and a magneto-resistive (MR) head for reproducing signals are integrated. ").

In the position error signal generator 8, the MR head 2
From the servo signal 11 obtained from the surface of the disk 1,
As a triangular wave signal having one cycle in two tracks, a position error signal 12 indicating position error information between the MR head and the center of the data track is generated.

The position error signal 12 is converted into a digital signal by an analog-digital converter 10 (ADC: Analog-Digital Converter), and the correction value calculator 6 of the DSP 4
The corrected position error signal 16 is input to one input terminal of the controller 7. Control signal output from controller 7
17 is a digital-analog converter 9 (DAC: Digital)
-Analog Converter) converts the current to an analog signal and drives the actuator 2 to move the head 2.
18 is input to the actuator 3.

The drive current signal 18 of the actuator 3 is supplied to an analog-digital converter 10 '(ADC: Analog-Digital).
tal Converter) to convert to digital signal and DS
The other input terminal is input to the controller 7 of P4. The controller 7 of the DSP 4 generates a control signal 17 for the actuator 3 based on these signals.

First, an example of a method for generating the position error signal 12 from the servo signal 11 will be described.

As shown in FIG. 3, the servo signals 11 are discretely arranged on the data tracks of the disk 1. As the position error information, a burst signal as shown in FIG. Have been.

The integrated value of the peak value of the burst pattern or the integrated value of the burst pattern (referred to as "burst value") is obtained for A, B, C, and D bursts, respectively.

FIG. 5 shows a burst value when the head 2 is moved in the radial direction.

Referring to FIG. 5, when the values of (A burst)-(B burst) and (C burst)-(D burst) are obtained for each burst value, a two-phase position error signal is obtained. .

The two-phase position error signal 12 generated by the position error signal generator 8 is converted into a digital signal 13 by the analog-digital converter 10 and taken into the DSP 4.

The position error signal 13 captured by the DSP 4
Is selected by a selection signal (not shown), is used as position error information 19 as shown in FIG. 5, and generates head position information together with track information obtained by an address signal or the like recorded on the disk surface 1.

In the position error signal 12 generated as described above, the position error signal 12 generated by the servo signal 11 obtained from the disk surface 1 by the MR head is generally, as shown in FIG. The relationship between the head position error and the position error signal (referred to as “slope”) is non-linear.

Therefore, it is difficult to adjust the inclination near the center of the track only by adjusting the amplitude of the position error signal.
It is necessary to know the tilt near the center of the track, shown as 12.

However, when the offset seek and settling characteristics are considered, the error between the actual position error signal and the linearized position error signal increases as the distance from the track center increases, as shown in FIG. When the switching of the position error signal occurs, a step-like variation occurs.

Therefore, it is desirable to make further correction based on the inclination information near the switching of the position error signal.

Referring to FIG. 7, this correction method will be described below. In this case, as shown in FIG. 7, almost sufficient correction is possible.

In the magnetic disk drive, the head position can be detected only from the position error signal, so that it is difficult to detect the relationship between the head position and the position error signal. Therefore, means for directly measuring the head position is required.

In the step of writing the servo signal 11 to the disk 1, the head position can be directly measured by a head position detecting device using a rotary encoder 20 (see FIG. 1) used for positioning the head.

In FIG. 1 showing a simple example of the STW, the reference head 21 writes a servo clock for one track for writing a servo clock, and uses this as a reference clock.

The reference head 21 is used only in the step of writing a servo signal on the disk 1, and is removed after the end.

The self head (magnetic head) 2 is
A servo signal 11 is also written by using a self-head 2, which is a recording / reproducing head incorporated in the apparatus.

In the step of writing the servo signal 11 on the disk 1, the self-head 2 is connected to the rotary encoder 20 by an arm and positions the head by the rotary encoder 20, and after completion, the rotary encoder 20 is removed. Removed.

In such an apparatus, the head is finely moved near the track center, and the head position at two points and the position error signal generated from the servo signal 11 detected by the MR head as shown in FIG. By measuring, a linearized signal as shown in FIG. 6 is obtained. At this time, for example, a sine-wave noise is generated by the DSP 4, and the sine-wave noise is superimposed on the drive current signal 18 of the actuator to vibrate the head.
The magnitude of the position error signal having the same frequency component as the sine wave noise added to the above may be obtained. In this case, since the head position is the second-order integral of the drive current, the amplitude of the head position is proportional to the sine wave noise, and the proportional gain between the head position and the drive current of the actuator 3 is determined in advance by the characteristics of the actuator 3 and the like. Therefore, the magnitude of the same frequency as the position error signal and the drive current at the head position can be measured by the drive current that moves the head slightly near the center of the track. The drive current is varied, and the head position and the position error signal at several points are measured to calculate the variation rate.

The head position and the variation rate of the position error signal are written as information to a guard band area other than the data area on the disk 1 or the memory 5, and the information is used at the time of the servo operation, as shown in FIG. The correction is performed by using a typical position error signal.

In this case, although the actual position error cannot be obtained, the fluctuation rate between the virtual position error and the actual position error becomes almost equal near the track center, so that the track following characteristic is improved.

[0044]

[Embodiment 2] The method described in the above embodiment has the advantage of requiring less information, but as described above, the error increases when the position error signal is switched.

Therefore, as a second embodiment of the present invention,
As shown in FIG. 6, not only the fluctuation rate of the head position and the position error signal at the track center, but also two points near the position error signal switching point are measured and the fluctuation rates are stored as shown in FIG. Then, the method of correcting with three straight lines is more effective. That is, the drive current signal 18 of the actuator is passed so as to vibrate the head 2 to the switching point at which the position error signal is switched and used, and the head position and the position error signal near the position error signal switching point are measured at two points to be changed. Find the rate.

Further, with respect to the fluctuation due to the head position,
Information can be written on guard bands on the inner and outer sides of the data area and tracks not used as data writing tracks in the data area, and correction can be made by complementing the information between them, thereby deteriorating data efficiency. Embedded in the servo sector is more effective.

When the memory 5 is used, arbitrary information of several points can be stored.

According to the present embodiment, a more accurate head position can be obtained using the corrected position error signal, and the head can be obtained by the non-linearity of the position error signal due to the servo signal detection by the MR head. It is possible to reduce the deterioration of the positioning characteristics and the deterioration of the seek characteristic due to the influence on the head speed obtained by the deviation of the head position and the head position during the seek operation. In the offset seek operation, a desired offset amount can be given to the head.

Although the present invention has been described with reference to the above embodiments, the present invention is not limited to the above embodiments but includes various embodiments in accordance with the principle of the present invention.

[0050]

As described above, the present invention (claim 1)
According to the method, the variation rate information between the head position and the position error signal near the track center is obtained in advance, and the information is used at the time of the servo operation, and the correction is performed using the virtual position error signal. In the vicinity, the rate of change between the virtual position error and the actual position error becomes substantially equal, so that there is an effect that the track following characteristic is greatly improved. In the present invention (claim 1), the storage capacity required to store the fluctuation rate information can be particularly small.

According to the present invention (claim 1), a more accurate head position can be obtained by using the corrected position error signal, and the position error signal obtained by detecting the servo signal in the MR head can be obtained. Of the head positioning accuracy due to the non-linearity described above, and the deterioration of the seek characteristics due to the influence on the head speed obtained by the deviation of the head position and the head position during the seek operation. In the offset seek operation, a desired offset amount can be given to the head.

Further, according to the present invention (claim 2), two points near the position error signal switching point are measured, the fluctuation rate is stored, and correction is performed by three straight lines, thereby correcting the corrected position. Using the error signal, it is possible to obtain a more accurate head position.

Further, according to the present invention (claim 3), the fluctuation rate information is recorded on the disk surface, in particular, the guard bands on the inner and outer peripheral sides of the data area, and the tracks not used as data write tracks in the data area. For example, information can be written in each of them, and the gap between them can be complemented to make correction possible.

According to the present invention (claim 4), since information on the fluctuation rate at arbitrary points can be stored, the accuracy of correction of the non-linear characteristic is further improved, and the positioning accuracy of the head is improved. The seek characteristics can be improved.

According to the present invention (claim 5), a sine wave noise can be easily generated by the operation of the DSP mounted in the magnetic head device and can be added to the drive current of the actuator. There is an effect that a drive current of a degree of slight movement is supplied to the actuator to simplify the measurement process of the position error signal and improve the measurement accuracy.

[Brief description of the drawings]

FIG. 1 shows a servo track writer (ST) according to the present invention.
FIG. 14 is a diagram showing a configuration of W).

FIG. 2 is a diagram showing a configuration of one embodiment of the present invention.

FIG. 3 is a schematic diagram of a servo sector of a data surface servo.

FIG. 4 is a diagram illustrating an outline of a burst signal.

FIG. 5 is a diagram for explaining generation of position error information.

FIG. 6 is a diagram illustrating a state of correcting a position error signal according to one embodiment of the present invention.

FIG. 7 is a diagram illustrating a state of correcting a position error signal according to another embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 magnetic disk medium 2 magnetic head 3 actuator 4 DSP (digital signal processor) 5 memory 6 correction value calculator 7 controller 8 position error signal generator 9 digital-analog converter (Digital-Analog)
Converter 10,10 'analog-digital converter (Analog-Di)
gital Converter) 11 Servo signal 12 Position error signal 13 Position error signal (digital signal) 14 Correction value signal 15 Correction value signal 16 Position error signal after correction 17 Actuator control signal (Digital signal) 18 Actuator drive current signal 19 Position Error information 20 Rotary encoder 21 Reference head

Claims (5)

(57) [Claims] A servo signal obtained from said disk surface by said MR head, comprising: one or more magnetic disk media; and a composite magnetic head for recording and reproducing data by integrating an inductive head and an MR head. A position error signal generator for generating a position error signal indicating position error information between the MR head and the center of the data track as a signal having one period in two tracks or four tracks, and converting the position error signal into a digital signal In a magnetic disk drive that converts the input signal into a digital signal processing device and generates a control signal for an actuator that moves the head by the digital signal processing device, in the step of writing a servo signal on the disk surface,
For the position error signal generated by the servo signal detected by the MR head with respect to the head position detected by the head position detection device near the center of the data track, two to several points are detected and a linear function is detected. Writing the fluctuation rate information approximately obtained as storage means, and at the time of operation, using the fluctuation rate information to correct at least the gain of the position error information input to the digital signal processing device. position error correcting how the magnetic disk device according to claim. 2. A digital signal processor comprising: a position error signal generator for generating a position error signal indicating position error information between the MR head and the center of the data track as a two-phase triangular wave signal; A magnetic disk drive that switches a position error signal and uses the position error signal as position error information, wherein not only the fluctuation rate of the head position and the position error signal near the center of the data track, but also the fluctuation rate at a position error signal switching point. written in advance, by switching the three volatility, the position error correcting how the magnetic disk device according to claim 1, wherein the correcting the gain of the position error information. 3. The method according to claim 1, further comprising the step of writing a servo signal on the disk surface, wherein the change rate approximately obtained as a linear function is written in the memory. position error correcting how the magnetic disk device according. 4. A positional error correcting how the magnetic disk device according to claim 1 or 2, wherein said storage means is characterized by comprising the disk surface. 5. A step of writing a servo signal on the disk surface, wherein the digital signal processing device generates sine wave noise, and superimposes the sine wave noise on a drive signal of an actuator for moving the head. 2. The magnitude of a position error signal having a frequency component substantially the same as the sinusoidal noise added to the drive signal of the actuator is obtained by vibrating the position error signal near the center of the track.
Position error correcting how the magnetic disk device according.