JPS6199978A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To suppress an off-track, and to decrease the average data access time by executing the positioning of a data head by two pieces of servo- information. CONSTITUTION:For instance, two servo-heads 1, 8 are positioned on A and D, respectively, and separated from each other by a distance L. In this state, it can be presumed that data heads 2, 3 are positioned on C which is separated from A by L1 and D by (L1+L2=L), and data heads 4, 5 are positioned on B which is separated from A by L3 and from D by L4 (L3=L4, L3+L4=L). For instance, in case when the data head 2 or 3 is positioned on some line X, the data head 2 or 3 can be positioned exactly by shifting and positioning consciously the servo-head 1 and 8 to the inside by L2 from X, and to the out side by L1, respectively. In this case, from a position relation of the data head to be used and two servo-heads, the weight of two servo-information which is read by two servo-heads is determined, and the positioning is executed by using the two-servo-information by an appropriate ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a positioning system for a magnetic disk drive, and particularly to a positioning method suitable for a magnetic disk drive with high track density.

[Background of the invention]

Generally, a magnetic disk drive has a servo disk and a servo head for positioning the magnetic head, but if multiple disks stacked on a spindle are tilted due to thermal displacement, it may be difficult to accurately position the magnetic head. It had some problems.

Incidentally, a related device is disclosed in Japanese Patent Application Laid-Open No. 150105/1983.

[Purpose of the invention]

The purpose of the present invention is to increase storage capacity by using servo information read by two servo heads per actuator, suppressing the adverse effects of thermal displacement of the mechanical system, and making it possible to increase track density. Another object of the present invention is to provide a magnetic disk device that reduces the number of times data is reread by reducing servo off-track, and as a result, speeds up data access.

[Summary of the invention]

When multiple magnetic heads are attached to a carriage, the magnetic head at one end of the magnetic head group is generally used as a servo head to read servo information, and positioning is performed based on this, so the position of the magnetic head at the other end is It is most affected by adverse effects such as thermal displacement, and is easily off-track (
Become. In order to compensate for this, the servo head is
The positioning of the data head in between is performed using the information obtained from the two servo information and the positional relationship of the data heads.This suppresses off-track and achieves high track density. The effective average data access time is reduced because the probability of unreadability is low (and the number of rereads is reduced).

Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows magnetic heads 1 to 8. This is an example showing the relationship between head arms 11-15 and magnetic disks 21-24. Among the magnetic heads 1 to 8, one of the magnetic heads 1 to 8 is normally used as a servo head and the other as a data head, and positioning is performed using one servo head, but in the present invention, both magnetic heads 1.8 are used as servo heads. Positioning is performed as follows.

FIG. 2 shows an example of the deviation due to thermal displacement of the components shown in FIG. 1. If only the magnetic head 8 were used as a servo head as in the conventional system, the data head farther from 8 would have a larger deviation. In the present invention, since the magnetic heads 1 and 8 at both ends are servo heads, it is possible to position the data heads 2 to 7 at appropriate positions. Now, suppose that two servo heads 1 and 8 are located on A and D, respectively, and are separated by a distance. In this state, databeds 2 and 3 are located at C, which is Ll from the person and L2 (Ll +L2-L) from D.
Above, the data heads 4, 5 are from A to L5. D to L4 (
M, L5■L4. It can be expected that it is located on P, which is a distance of L5+L4 (L). Also data head 6.7
Similarly, its position can be predicted. As can be seen from Figure 2, if you try to position data head 2 or 5 on a certain line It can be seen that it is possible to accurately position the data head 2 or 3 by this.

In the present invention, the weight of the two servo information read by the two servo heads is determined from the positional relationship between the data head and the two servo heads used, and positioning is performed using the two servo information in an appropriate ratio. In FIG. 2, the number between helad arms is four. If the data head 2 or 3 is to be positioned at a certain position, the servo information read by the servo heads 1 and 8 will be 3/4.1/3/4.
It would be better to use 4 each.

Can be positioned.

Figure 3 shows position error No. 6 (PE8). P.E.
S is a signal representing the positional deviation of the servo head created by the servo head reading the servo information K, and when the servo head is located at the track center QK, PE8 is [
v]. At this point, the servo head shifts to the left by L5,
Luto located on P E S HAV's (V ] (
Vt<O).

Also, if it shifts to the right by L6 and is located on R, V2 (V) (
V*>o). Therefore, the direction and amount of positional deviation of the servo head can be detected by PES.

The relationship between the PES and the position of each head in the present invention is shown below in FIGS. 4 and 5. Here, it is assumed that the servo information to be read by the servo heads 1 and 8 is mossed at the same position on each servo surface. Therefore, if two servo heads are in the same position, the PES produced by them will be exactly the same signal.

FIG. 4 shows a state in which there is no displacement of each head. The top is P
ES, the bottom eight ports each indicate a head, and the numbers correspond to each head number.

In this figure, the servo heads 1 and 8 are located at the track center, and the two PEs 8 are both 0 [v].

FIG. 5 shows a case where each head is misaligned due to thermal displacement of mechanical parts or the like. By positioning two servo heads on S and T as shown in the figure, two PES
A potential difference ■5 [■] occurs between them, and the PES of the two servo heads is 4V3 (V) (V3)O), V4 (V) (V
4(0)-ic-(V3-V4-V5). Also,
If data heads 2 and 3 are positioned at the track center, and if data head 2 or 3 is a servo head, its PES should be 0 [v]. It can be seen from this figure that within the range where the linearity of PES can be almost maintained, data heads 2 and 3 can be accurately positioned at the track center by positioning -1v3+V4 (-0) as PES. It turns out that data positioning can be done in the same way.

FIG. 6 shows an example of the circuit of the present invention. Servo head 31.3
PES generation circuit 33.3 from the servo information read in 2.
4 produces two PH8s. Two PESs and two signals corresponding to the position of the head bar generated by the PE8 controller 36 from the head selection signal are respectively sent to the multiplier 3.
Multiplied by 5.36. The sum of the outputs of multipliers 55 and 56 is sent to servo controller 38. In addition to this, servo control signals such as a seek command are applied to the servo controller 38. Servo controller 3
The output of 8 is amplified by a power amplifier 39, and the carriage 4 is equipped with a series of heads including servo heads 31 and 32.
1 is driven by a VCM (voice coil motor) 39. In addition to always using two servo heads for both seek and track following as in this example, we are also considering using only one servo head during seek and two servo heads only during track following. It will be done.

〔Effect of the invention〕

According to the present invention, servo off-track due to thermal displacement can be significantly reduced, making it possible to increase track density and reduce the number of data re-reads due to servo off-trunk, resulting in a reduction in average data access time. I can do it. Furthermore, since the number of magnetic disks per actuator can be increased, pit costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between a magnetic head, a head arm, and a magnetic disk, and FIG. 2 is a diagram showing an example of a circuit according to the present invention. 1-8...Magnetic head, 11-15...Head arm, 21-24...Magnetic disk, 31.32...
Servo head, 53.34...Servo amplifier, 3shi3
6...Low pass filter, 57.58...Multiplier,
39... Decoder, 40... Subtractor, 41... Divider, 42... Servo controller, 43... Power amplifier, 44... Voice coil motor, 45...
carriage. Fig. 1 Fig. 2 J 5', 23 I L3 L4 Fig. 3 Q SQ Ding Vj6 Fig.

Claims (1)

[Claims] In a magnetic disk drive that has two servo heads per actuator and positions the data head using servo information read by each of the two servo heads, the position of the data head used is determined based on the servo information read by each servo head. 1. A magnetic disk drive characterized in that accurate positioning that is less susceptible to thermal displacement is performed by assigning weights to each of the two pieces of servo information and positioning by combining the two pieces of servo information.