JPH05298840A - Magnetic disk driving device - Google Patents

Abstract

PURPOSE:To continuously obtain position signals without saturation and to speedily and stably perform a head positioning by superimposing positioning information in a tracking direction and making the superposing width to be a difference between a track pitch and a track width. CONSTITUTION:Among many pieces of burst information 12 for a magnetic head positioning, A burst 12a, B burst 12b, C burst 12c and D burst 12d are superimposed in a track direction, respectively. Moreover, the width of the superposition is made to the difference between the track pitch Tp and the track width Tw, i.e., Tp-Tw. In such an arrangement, when the magnetic head is deviated from the center of a track and even if the amount of the deviation exceeds a half of the track width Tw, the magnetic head reads the two pieces of information of the positioning information 12, the position signals are obtained based on the results of the reading and are not saturated and normally obtained, therefore, the head is speedily and stably positioned.

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 used for an external storage device of a computer system, and more particularly to a magnetic head positioning control in the device.

[0002]

2. Description of the Related Art A magnetic disk drive device reads / writes data by positioning a magnetic head at a desired data position on a magnetic disk rotating at a high speed at a high speed. As a positioning method for this magnetic head,
Conventional magnetic disk drive devices have mainly adopted a servo surface servo system having a magnetic head dedicated to positioning and a magnetic head dedicated to data. However, recent magnetic disks that require smaller size, lighter weight and higher density In the drive device, the sector servo system is often used. The sector servo method is a method in which positioning information is written on the data surface of a magnetic disk and then read by a magnetic head to perform positioning control.As with the servo surface servo method, a magnetic head for positioning and a magnetic head for data are used. There is an advantage that it is not necessary to prepare the head separately.

In an access motor for driving a magnetic head,
Due to the demand for smaller size, lighter weight, and higher speed, there is a tendency not to attach a position detector. Instead, the magnetic head uses a discrete time control method that uses only servo information for each sector that has been written in advance on the magnetic disk. High speed access and precision positioning.

FIG. 4 is a plan view showing a magnetic disk drive device. In the figure, the magnetic head 1 is an actuator 2
The actuator 2 is attached to the front end of the actuator 2 and is rotated by a voice coil motor 3 about a fulcrum 4. The magnetic head 1 moves on the magnetic disk 5 as the actuator 2 rotates. The magnetic disk 5 is rotationally driven by a spindle motor 6. Further, N sector parts 7 are provided radially on the magnetic disk 5 at equal angles, and burst information is written in the sector parts 7 as servo information for controlling the magnetic head 1.

FIG. 5 shows burst information. In the figure,
The magnetic head 1 scans in the direction of arrow a and reads the A burst and B burst or the C burst and D burst to detect the position of the magnetic head 1. For example,
To detect the position of the magnetic head 1 near the (n + 1) track, the A burst and the B burst are read and (n
+2) To detect the position near the track, read the C burst and D burst. When obtaining the position of the magnetic head 1 from the reading result, assuming that the obtained position is x, x = (A−B) / (A + B−2m) (1) or x = (C−D) / (C + D−2m) ) (2) Here, m is a noise value.

[0006]

However, the above-mentioned conventional device has a problem that the position signal is saturated in position detection by burst information reading. Figure 5
And it demonstrates using FIG. FIG. 6 is a graph showing the relationship between the displacement amount of the magnetic head 1 and the position x.

In FIG. 5, track width (reading width)
Is Tw and the track pitch is Tp, the magnetic head 1
The relationship between the position x and the actual shift amount is as shown in FIG. 6 from the above equation (1). When the magnetic head 1 is near the center of the (n + 1) track, x takes a normal value, but when the magnetic head 1 deviates from the center of the track by Tw / 2 or more, only A burst or B burst is read. Therefore, the position signal x is saturated as shown in FIG. Deviation amount T
The value w / 2 is Tw / 2 when expressed in track units.
It becomes Tp [track], and Tw
Since the relationship is ≦ 0.8 Tp, the deviation amount is (Tw / 2T
p) <0.5, which is less than 1/2 [track].

Precise positioning control of the magnetic head 1 is performed using this position signal x, but one track seek (1
In the case where a signal for moving one track is given as an input (movement control of only track), the position signal x saturates at 1/2 [track] or less, so after the magnetic head is displaced by Tw / 2 or more, Correct input cannot be obtained.
As a result, there is a problem that the control becomes unstable.

Further, when the speed control of the magnetic head (control for moving the magnetic head to the target track) is shifted to the position control (control for positioning the magnetic head on the target track), overshoot (passing) with respect to the target track. May extend over several tracks, the position signal x
If it is saturated below 1/2 [track], not only will the control become unstable, but it may also become impossible to control.
It was a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to arrange a burst information in a sector portion and to read a track detection information at the time of position detection to obtain a normal position signal. It is an object of the present invention to provide a device for continuously controlling the positioning of the magnetic head by stably obtaining the above.

[0011]

In order to solve the above problems, the present invention has track detection information and magnetic head positioning information as servo information on a magnetic disk, and reads the positioning information. In a magnetic disk drive that detects the position of a magnetic head, the positioning information is composed of two pieces of information that are shifted in a direction substantially orthogonal to the tracking direction and overlap in the tracking direction. The overlapping width in the tracking direction is a track pitch and a track width. Is the difference between the two.

[0012]

[Operation] When the magnetic head is displaced from the center of the track,
Even if the amount of deviation exceeds half the track width, the magnetic head can read both pieces of positioning information, and the position signal obtained based on the read result can be normally obtained without being saturated. Since the two pieces of the positioning information that are offset from each other overlap by the difference between the track pitch and the track width, the position signal can be normally obtained until the shift amount of the magnetic head becomes half the track pitch.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Note that elements common to the drawings are given the same reference numerals. FIG. 1 is an explanatory diagram showing an arrangement of Gray code information and burst information as servo information in the embodiment,
FIG. 2 is a block diagram showing a control circuit of the magnetic disk drive device in the embodiment.

In FIG. 1, gray code information 11 is information for detecting the position of the magnetic head 1 in track units, and is written together with burst information 12 in the sector portion 7 on the magnetic disk 5 shown in FIG. .. The burst information 12 includes A burst 12a and B burst 12
b, a C burst 12c and a D burst 12d are arranged so as to overlap each other in the tracking direction.
Assuming that the track width is Tw and the track pitch is Tp, the width of each burst 12a to 12d exceeding the track center is (Tp-Tw) / 2.
2a and B burst 12b overlap width (C burst 12c
And the width at which the D burst 12d overlaps) is (Tp-Tw).

In FIG. 2, the magnetic head 1 is an amplifier 1
3. An analog / digital (A / D) converter 14 and a control unit (μCPU) 15 are connected in this order. In the controller 15, a position detector 15a and a compensator calculator 1 are provided.
5b is provided. The controller 15 controls the voice coil motor 3 via the digital / analog (D / A) converter 16 and the voice coil motor (VCM) driver 17.
It is connected to the.

Next, the operation of this embodiment will be described.

When the magnetic disk drive is activated, the spindle motor 6 rotates the magnetic disk 5 at a high speed.
The magnetic head 1 is moved on the magnetic disk 5 by the voice coil motor 3. At this time, the magnetic head 1 reads the gray code information 11 and the burst information 12 of the sector section 7. The read information is converted into an electric signal by the magnetic head 1 and sent to the amplifier 13. After being amplified by the amplifier 13, it is converted into a digital signal by the A / D converter 14 and sent to the position detection unit 15 a in the control unit 15.
The position detection unit 15a detects the position of the magnetic head 1 from the read signal of the burst information 12, and the detection is performed by x = (A−B) / (A + B−2m) (3) or x = (C−D ) / (C + D-2m) (4). Note that m is a noise value.

Here, the track width Tw and the track pitch T
When the ratio of p is 2: 3 and the noise m = 0, the relationship between the position x obtained by the equation (3) or the equation (4) and the actual shift amount of the magnetic head 1 is shown in FIG. FIG. 3 shows a case where the magnetic head 1 is displaced from the center of the (n + 1) track in the n track direction. For example, the magnetic head 1 shown by a broken line in the figure is displaced by 1/6 [track] in the n track direction. And x at this time becomes 1/3. When the deviation of the magnetic head 1 is 1/6 to 1/2 [track], the relationship between x and the deviation amount is non-linear, but the error is small. It can be seen from FIG. 3 that the position signal x
Means that the magnetic head 1 does not saturate until the deviation amount of the magnetic head 1 becomes 1/2 [track].

Next, the position detection will be described.

Now, suppose that the magnetic head 1 is on the straight line b in FIG. 1 and the position from the n track is obtained. The scanning of the magnetic head 1 is in the direction of the arrow of the straight line b. The magnetic head 1 first reads the gray code information 11. The gray code information 11 indicates a track number, and since the reading center of the magnetic head 1 is on the straight line b, the position in track unit is detected as (n + 2) −n = 2 [track].

Next, the burst information 12 is read. When the magnetic head 1 passes near the (n + 2) track,
The position is detected by reading the C burst 12c and the D burst 12d. Therefore, the position x _p from the center of the (n + 2) track is expressed by the following equation (4): x _p = {(C−D / (C + D−2m)} × 1/2 [track] (5) 1/2 is a constant for converting the position into track units, and this constant is obtained from Fig. 3. Therefore, the position x from the n track is x = 2 + {(C-D / ( C + D-2m)} × 1/2 [track] (6)

The position signal obtained by the position detecting section 15a as described above is sent to the compensator calculating section 15b. The error between the calculated position and the target position is calculated in the preceding stage of the compensator calculating section 15b. The compensator calculation unit 15b calculates an operation amount according to the error. Operation amount is D / A converter 1
After D / A conversion in 6, the voice coil motor drive unit 1
7 to drive the voice coil motor 3. Thereby, the positioning control of the magnetic head 1 is performed.

As described above, the burst information 12 is arranged so that the position signal is not saturated until the magnetic head 1 is displaced by 1/2 track, and the gray code information for track detection is also read at the time of position detection. Even at a position several tracks away from the target track, the detected position signal is continuously obtained without being saturated.

[0024]

As described above in detail, according to the present invention, since the burst information 12 is arranged so that the position signal is not saturated until the magnetic head 1 is displaced by 1/2 [track], the position signal is saturated. It is possible to continuously obtain the magnetic head 1, and to expect high-speed and stable positioning control of the magnetic head 1.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an arrangement of Gray code information and burst information in an embodiment.

FIG. 2 is a block diagram showing a control circuit of the magnetic disk drive device according to the embodiment.

FIG. 3 is a graph showing the relationship between position x and displacement amount.

FIG. 4 is a plan view showing a magnetic disk drive device.

FIG. 5 is an explanatory diagram showing burst information.

FIG. 6 is a graph showing a relationship between a position x and a shift amount in a conventional example.

[Explanation of symbols]

 1 Magnetic Head 5 Magnetic Disk 7 Sector Section 11 Gray Code Information 12 Burst Information 15 Control Section

Claims (1)

[Claims] 1. A magnetic disk has track detection information and magnetic head positioning information as servo information,
In a magnetic disk drive that detects the position of a magnetic head by reading the positioning information, the positioning information is composed of two pieces of information that are shifted in a direction substantially orthogonal to the tracking direction and overlap in the tracking direction. The magnetic disk drive device, wherein the overlapping width is the difference between the track pitch and the track width.