JPH04283411A - Magnetic head position control method for magnetic recording devices - Google Patents

Abstract

PURPOSE:To shorten the head switching time by preliminarily correcting a track offset amount caused by the difference of a core width between plural magnetic heads in the data servo type head positioning system of a magnetic disk device. CONSTITUTION:At the time of a first STW writing, pieces of servo information 21 and 22 are written by successively shifting the core 19 of an (a) head and the core 20 of a (b) head (the difference of the core width 18) by every a half of track width(P/2). At the time of reading a track 21, a head 19 is controlled so as to follow the center of the 21, and at the time of reading a track 22, a head 20 is controlled so as to follow the center of the 22 so that it is necessary to move the head by an offset amount (x) at the time of switching the head. When this value (x) is measured, and the second STW writing is operated to the head (b) by adding the value (x), the position and the track at the time of the writing and reading of the head (b) are respectively 205 and 220 and it is not necessary to move the offset amount (x) at the time of switching the head.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head position control method for a magnetic recording device, and more particularly to a magnetic head position control method for a magnetic recording device that uses a data servo control method to cause a magnetic head to follow a track of a rotating recording medium such as a magnetic disk. This invention relates to a head position control system.

0002

[Prior Art] Conventionally, for example, U.S. Pat. No. 4,371,
As described in the specification of No. 960, a plurality of magnetic heads for each recording surface of a plurality of magnetic disks are attached to the same carriage, the magnetic heads are moved to a target track by a seek command, and the magnetic heads are moved to a target track. A known method is to compensate for offsets caused by installation errors in the radial direction (track width direction) of each magnetic head in the magnetic disk radial direction (track width direction). In this method, one of the multiple disk surfaces is dedicated to servo (servo disk),
The remainder is a data disk, and the deviation (installation error) of each data head (magnetic head relative to the data disk) from the servo head (magnetic head relative to the servo disk) in the track width direction is measured in advance, and this measured value is used as the offset for each data head. By storing this offset amount in memory as an amount, and when performing actual track following control, reading this offset amount from memory and adding it to the servo system, it is possible to eliminate the influence of installation errors and make the data head follow the center of the track. I have to.

0003

[Problems to be Solved by the Invention] The above-mentioned prior art takes into account the elimination of the influence of mounting errors between the servo head and the data head in the servo surface servo control method (method using a dedicated servo disk and servo head). However, in the data servo control method (a method that does not have a dedicated servo disk and servo head, each disk surface contains data information and servo information, and uses this servo information to control the track following of the data head), No consideration is given to the problem of offset occurring due to differences in core widths (dimensional differences, variations). This problem will be explained using FIGS. 2(a) and 2(b).

[0004] In the data servo control system, normally,
Servo information is written at the beginning of each sector in each track of each disk, and data information is written at a position following the servo information. From now on, the servo information writing function will be referred to as ``servo track writing'' (abbreviated as ``STW'').
”). Further, hereinafter, "writing" and "reading" of servo information and data information may also be referred to as "recording" and "reproducing". The servo information and data information are written by partially overlapping each other by sequentially shifting the magnetic head in the radial direction of the magnetic disk by 1/2 track pitch.

FIG. 2(a) is a top view showing the state in which servo information is written, and 19 and 20 are magnetic heads (a and b) located on separate magnetic disks. 191 and 192 are one side and the other side of the core of the magnetic head 19, and 201 and 202 are one side and the other side of the magnetic head 20. The magnetic heads 19 and 20 have different core widths Wa and Wb (Wa>Wb in this example), respectively, and are simultaneously driven in the disk radial direction (track width direction) by the same actuator. 1
8 shows the difference in the core width Wb of the magnetic head 19 in one place for convenience and is shown as the difference e between the one side portions 191 and 201. Therefore, the other side portions 192 and 202 of the core are shown together. However, in general, this is not always the case. Also, head installation errors generally occur when the head 19
It is expressed as the difference between the center of the core width of the head 20 and the center of the core width of the head 20, but here, the difference δ(
The center-to-center core width is shown as half of that. This δ and the above e are generally independent and do not match. 21 is a track written by the magnetic head (a) 19;
2 is a track written by the magnetic head (b) 20, which contains track center following information (i.e., servo information) c and track center following information (i.e., servo information), respectively.
d is written. 211, 212, and 213 are one side edge, center line, and other side edge of the track 21;
2 and 223 are one side edge, center line, and other side edge of the track 22.

When writing servo information c to the track 21, first, write the line 2 at the head core a position in FIG. 2(a).
Write with a width Wa below line 212, then write with a width Wa below line 212 with the head core a moved downward by half the track pitch P (P/2) (at this time, it overlaps with the current write). (The previously written portion is erased), and then, with the head core a further moved downward by P/2, writing is repeatedly performed below the line 213 with a width Wa. As a result, tracks 21 having a center of 212 and a track width of P (<Wa) are successively formed. Similarly, the magnetic head 20 whose pitch moves integrally with the magnetic head 19 by P/2 allows the track center to be 222, the track side edges to be 221,
At 223, a track 22 with track width P is formed.

FIG. 2(b) shows a state in which the servo information written in FIG. 2(a) is read. Now, when the magnetic head 19 is selected to read the track 21, the magnetic head 19 is subjected to track following servo, so the center of the core width of the head 19 is aligned with the center line 2 of the track 21.
Following is controlled to match 12. At this time, the position of the magnetic head 19 relative to the track 21 is displaced upward in the figure by xa=(Wa-P)/2 compared to FIG. 2(a), and the magnetic head 20 is also displaced upward by the same distance. However, the center of the core width of the unselected magnetic head (b) 20 does not necessarily coincide with the center of the track 22.

Next, from the magnetic head 19 to the magnetic head 20
(select magnetic head 20) and select track 2.
2, the magnetic head 20 is subjected to following servo so that the center of the core width of the magnetic head 20 coincides with the center line 222 of the track 22. At this time, the position of the magnetic head 20 with respect to the track 22 is , Figure 2
As a result, the center of the core width of the non-selected magnetic head 19 is displaced upward in the figure by xb = (Wb-P)/2 compared to (a), and the magnetic head 19 is also displaced upward by the same distance. It no longer coincides with the center line 212. Therefore, when the magnetic head is changed from 19 to 20 or from 20 to 19, the magnetic head assembly is
In the track width direction, the difference between the above displacements xb and xa is x=xb-
It must be displaced upward or downward (towards the outer circumference or inner circumference in the track width direction) by a distance equivalent to xa=(Wb-Wa)/2=e/2 (this is referred to as the "offset amount x"). Must be. In the example of Fig. 2, Wa>Wb, so when switching the magnetic head from 19 to 20, it is displaced downward by the offset amount x, and when switching the magnetic head from 20 to 19, it is displaced upward by the offset amount x. There is a need. When Wa<Wb, the displacement direction is reversed. This offset amount x is directly related to the core width difference (Wb-Wa) between each magnetic head, and is not directly related to the installation error δ between each magnetic head. When there is this difference in core width, it takes time to control the head to follow the track during head switching, so there is a problem that the head switching time becomes long.

The inventors of the present invention have newly discovered that there is a problem that head switching time becomes longer due to this difference in core width between heads, and have attempted to solve this problem.

Therefore, it is an object of the present invention to overcome the problems of the prior art described above and shorten the switching time when switching magnetic heads by correcting in advance the offset amount based on the core width difference between each magnetic head. However, it is an object of the present invention to provide a magnetic head position control system for a magnetic recording device that improves throughput.

[0011]

[Means for Solving the Problems] In order to achieve the above object, the present invention, as its basic principle,
The offset amount caused by the core width difference (variation) is measured for each magnetic head, and when performing the actual seek servo, this offset amount is taken into account in the control system to correct the offset due to the core width difference. In this way, track following servo is performed for each magnetic head.

Specifically, the present invention comprises a plurality of rotating magnetic recording media (magnetic disks) and a plurality of magnetic heads that record or reproduce servo information and data on each recording surface of these magnetic recording media. an actuator that moves these magnetic heads together to an arbitrary track (cylinder) on the recording surface; and control so that the actuator moves the magnetic heads to a target track and follows the track during a seek. In a magnetic head position control method of a magnetic recording device having a seek control section, a difference in the core width of the magnetic head or an offset amount due to the difference in core width is measured in advance when recording servo information (STW). However, at the time of seek, the offset amount based on the core width difference is corrected to track the selected magnetic head.

In the preferred invention, first, the core width difference is measured for each magnetic head during the first recording of servo information (STW), and this measured value is taken into account when recording the servo information (second time). STW). In this second STW, the core width difference is taken into consideration, and the write position of the servo information in the track width direction is displaced from the first position by the offset amount caused by this core width difference, thereby correcting the difference. be done. The above-described first and second writing of servo information by STW is performed in the factory before shipment.

In addition, instead of the second STW described above, the difference between the heads (measured value) obtained by the first STW is stored in a microcomputer or a recording medium in a recording device in the factory, and the actual (user It is also possible to perform correction using this stored measurement value when switching heads during use (according to the above).

In any of the above examples, in addition to the conventional installation errors between heads and errors due to environmental changes such as temperature changes, it is possible to correct the offset amount due to the core width difference according to the present invention.

[0016]

[Operation] The operation based on the above configuration will be explained.

According to the present invention, in the data servo system, if there is a variation (disparity) in the core width between each magnetic head, it is possible to After switching, this difference or the amount of offset caused by it is measured, for example, as a reproduction voltage level (more specifically, the servo information by the first STW is written in each head, and this is immediately read out to measure the level, etc.). core width disparity can be measured by comparing). Then, during the second STW, the measured value representing the head core width difference obtained during the first STW is added as a correction value each time the head is changed, so that each magnetic head has a higher value than the first STW. The servo information is written by the STW at this displaced position. The above is done in the factory before shipping. Next, even if there is a change (switching) between magnetic heads with different core widths during actual use (seek time), the track on each magnetic recording medium surface is calculated in advance by taking into account the amount of offset caused by the difference in core width. Since the magnetic head is formed at a displaced position, the magnetic head can be caused to follow the track center without changing the magnetic head position before and after magnetic head switching.

[0018] Therefore, the magnetic head switching time is shortened, and
Throughput can be improved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to FIG. 1 and FIGS. 2(a) and 2(b).

FIG. 1 is a block diagram of an embodiment of the present invention. 1 is a rotating magnetic recording medium such as a magnetic disk mounted on a driving spindle; 2 is a magnetic head for recording or reproducing data on the rotating magnetic recording medium 1; A plurality of magnetic disks 1 are stacked on a spindle, and each magnetic head is provided for each recording surface of each magnetic disk 1. However, for simplicity, in the figure, one magnetic disk and one magnetic head are provided. Only one magnetic head is shown. These magnetic heads 2 are connected to a single actuator 3
The actuator 3 simultaneously drives the magnetic disk in the radial direction to position it on any track (cylinder). Actuator 3 is driven by actuator drive circuit 4 . The position detection circuit 5 detects the position of the magnetic head 2, and the output of the position detector 5 is input to a track following control section 7 for positioning the magnetic head 2 at the center of the track. The speed detector 6 detects the speed of the head 2, and the output of the speed detector 6 is input to the seek control section 8. The seek control section 8 outputs a drive signal for the actuator 3 based on the output of the speed detector 6 and the head movement speed command 10 sent from the microcomputer 9.

The offset detector 17 detects the amount of deviation of the head 2 from the track center, and sends the detected value to the host device (S
(including TW device) 13. The switch 11 receives a signal from the seek control section 8 when the seek signal 12 is on, and receives a signal from the track following control section 7 when the seek signal 12 is off, according to a command from the microcomputer 9, to the actuator drive circuit. Output to 4. As a result, a feedback loop is formed during both seek control and track following control, and the movement of the head 2 can be controlled.

In the device configured as described above, when writing the information for the head 2 to follow the track center, that is, the servo information (during STW), first, in the section [Problems to be Solved by the Invention], the following is explained. As described in 2(a) and 2(b), if there is a difference e between the core widths Wa and Wb between b, there will always be an offset amount x (=e/2)24.

Therefore, in this embodiment, after first writing the servo information by the first STW in a normal manner, this offset amount (x) 24 is written to the offset detector 1.
Detected by 7. (For example, the servo information pattern written as described above is composed of a set of signals having a fixed time difference from each other and having a width of 1 pitch P above and below from the center line 212 of the track 21. Therefore, the offset amount Xa,
Xb can be detected. This servo pattern and the method of detecting the offset amount are well known, so a detailed explanation will be omitted.) Next, using this detected value (measured value) x as information for tracking the track center, STW is performed again (that is, the second time) for each magnetic head. The second time,
Since the servo is applied in consideration of this detected value x, the magnetic head is followed to a position displaced by this value x compared to the first time. For example, if the magnetic head (a) 19 is considered as the reference (the track 21 by the magnetic head 19 remains as it was for the first time), then in the second time, the magnetic head b2
When 0 is selected, the core 205 of the magnetic head 20 is displaced upward by the value x compared to the first time, as shown in FIG. is displaced upward by a value x compared to .

[0024] As a result, during actual use, the
), the servo information can be read by making the magnetic head 20 follow the center of the track 220 while keeping the positional relationship of the magnetic head (b) 20 with respect to the magnetic head (a) 19 in the track width direction unchanged. , when switching from magnetic head 19 to magnetic head 20 or vice versa, the magnetic head can immediately follow the track, reducing switching time and improving throughput.

The detected value (offset amount) x is a value determined for each head, and is determined as a deviation from a certain head as a reference. The offset amount x may be detected (measured) at any track on each disk surface (for example, at the inner circumference, middle, outer circumference, etc.).

The work up to writing the servo information by the second STW is performed in the factory before shipping.

Instead of the second STW in the above embodiment, the difference between the heads (measured value) obtained by the first STW is stored in a microcomputer or a recording medium in a recording device in the factory, and then used by the user. When performing a head change at this time, it is also possible to perform correction using this stored measurement value.

In addition to the correction of the offset amount caused by the core width difference according to the present invention, it is also possible to correct the conventional magnetic head installation error in the track width direction and to correct environmental changes such as operating temperature. Of course.

In the above embodiment, a data plane servo system has been described, but it is obvious that the present invention is not limited to this and can be applied to a servo plane servo system. In this case, the servo head may be used as a reference head, and the core width difference between this and each data head may be compensated for individually.

[0030]

As described in detail above, according to the present invention, in the magnetic head position control method of a magnetic recording device using the data servo method, the amount of offset caused by the core width difference is measured in advance for each magnetic head. In addition, when switching the magnetic head using the seek servo, this offset amount is added to control the position of the magnetic head, which has the effect of shortening the head switching time and improving throughput. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is an operation explanatory diagram for explaining the operation of the present invention in comparison with the conventional technology.

[Explanation of symbols]

1 Magnetic disk (rotating magnetic recording medium) 2 Data magnetic head 3 Actuator 4 Actuator drive circuit 5 Position detector (of the magnetic head) 6 Speed detector (of the magnetic head) 7 Track following control section 8 Seek control section 9 Microcomputer 10 Speed command 11 Seek/track follow switch 12
Seek signal 13 Host device (STW device) 14 Seek command 15 Seek end report signal 16 Head position signal 17 Inter-head core width offset detector 18 Inter-head core width difference 19, 20 Magnetic head (a, b) 21, 22 Track ( Track center tracking information c, d
) 23 Magnetic head (a') 24 Offset amount (x) 191, 192 One side (of magnetic head a) and the other side 201, 202 One side and other side (of magnetic head b) 205 (Magnetic head b) cores 211, 212, 213 (of track 21) one side edge, center line, and other side edge 220 track (track center tracking information) d'22
1,222,223 One side edge, center line and other side edge (of track 22)

Claims (1)

[Claims] 1. A plurality of rotating magnetic recording media, a plurality of magnetic heads for recording or reproducing servo information and data on each recording surface of these magnetic recording media, and a plurality of magnetic heads that perform the recording together with the plurality of magnetic heads. A magnetic head position of a magnetic recording device having an actuator that moves to an arbitrary track on a surface, and a seek control unit that controls the actuator to move the magnetic head to a target track and follow the track during seek. In the control method, the difference in core widths of the magnetic heads is measured in advance when recording servo information, and the offset amount based on this core width difference is corrected at the time of seek to perform track follow-up control for the selected magnetic head. 1. A magnetic head position control method for a magnetic recording device, characterized in that the head position control method is configured as follows.