JP3259097B2 - Servo control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control system for controlling the positioning of a head with respect to a recording medium. A recording device using a magnetic disk, an optical disk, or the like as a recording medium is used for recording various types of information. In such a recording apparatus, the recording density is increased to achieve miniaturization or large capacity. To increase the recording density, one or both of the track density and the bit density on the track must be increased. When the track density is increased, it is necessary to increase the positioning accuracy of the head. Various methods have already been proposed for improving the positioning accuracy.

[0002]

2. Description of the Related Art In a conventional magnetic disk drive using, for example, a magnetic disk as a recording medium, a plurality of heads are positioned with respect to tracks (cylinders) on a plurality of recording surfaces of a magnetic disk by an actuator. In this case, a servo surface servo method in which one surface of the magnetic disk is a servo surface on which servo information is recorded, and the other surface is a data surface on which data is written or read, and a data zone and a servo are formed on which data is written or read. There is known a sector servo system in which servo zones on which information is recorded are alternately formed in a circumferential direction.

In the servo surface servo system, a servo head is provided on a servo surface, and an actuator is controlled based on servo information read out by the servo head so as to position the data head on the data surface on a target track. Therefore, when the number of magnetic disks mounted is small, the ratio of the servo surface to the entire recording surface increases. In the sector servo system, an actuator is controlled so that servo information in a servo zone is read by a head and the head is positioned on a target track. It can be used for recording.

[0004]

In the conventional servo surface servo system, a relative displacement between a plurality of heads positioned by an actuator may occur due to mechanical accuracy and temperature distribution. is there. In such a case, even if the servo head is positioned with high precision, a positioning error of the data head will occur. Particularly, when the track density is improved, even a slight error may cause a problem of crosstalk due to adjacent tracks. It has the disadvantage that it becomes larger and, in the worst case, causes read errors.

[0005] In contrast to the servo surface servo system, the sector servo system is a system in which each head reads servo information from a servo zone. Therefore, positioning is performed with high precision corresponding to a designated head among a plurality of heads. be able to. However, when data on the same cylinder is sequentially read only by switching the head or when data is written, repositioning is performed based on the servo information corresponding to the head. There is a drawback that the data reading or writing must be waited until the rotation is performed, and the processing speed is reduced. SUMMARY OF THE INVENTION It is an object of the present invention to position a head with respect to a recording medium with high accuracy and at high speed.

[0006]

The servo control system according to the present invention will be described with reference to the principle explanatory diagram of FIG. 1. In the servo control system, data is written to or read from a recording medium 1 such as a magnetic disk or an optical disk. Head 2 to perform and this head 2
And a fine movement actuator 4 such as an electrostrictive element corresponding to the head 2. The servo information recorded on the recording medium 1 is read out by the head 2. A servo control method for positioning on a target track, comprising:
Has a configuration in which the data zone 5 and the servo zone 6 are alternately formed at least in the circumferential direction, and the position of the servo zone 6 is shifted in the circumferential direction corresponding to the head 2,
A servo demodulation circuit for inputting servo information by sequentially switching the head 2 for reading the servo information of the servo zone 6 by a head switching circuit, and driving the actuator 4 in accordance with error information from the servo demodulation circuit to perform positioning control of the head 2. Error information from the servo demodulation circuit
And a control processing circuit for performing positioning compensation control by driving a driver of the fine movement actuator 4 in accordance with error information corresponding to the head 2 by performing switching by a driver switching circuit that performs switching control synchronously with the switching circuit. 7, a head arm; and 8, a spindle that rotatably supports the recording medium 1.

Further , one of the plurality of heads 2
The actuator 3 is controlled based on the read servo information.
To control the positioning of a plurality of heads 2
Based on the servo information of servo zone 6
The fine motion actuator 4 corresponding to the
A configuration for performing control is provided.

The head 2 is set in the access mode and the fine mode.
Tracking mode that follows the target track via the
From the access mode in the process of shifting to
Fine movement actuator 4 when shifting to fine mode
Is driven according to the error information corresponding to the head.
Things.

When the mode is shifted to the tracking mode,
Position error of the head to read the servo information at
Write or read data from the
Position error corresponding to head that reads servo information from bozone
The fine movement actuator of this head
Having a configuration for performing positioning compensation control by driving the motor 4
It is.

[0010]

The spindle motor with the spindle 8 not shown is omitted.
Fixed to this spindle 8 by rotating
One or more recording media 1 are rotated. This
Arranged on one side or both sides of the recording medium 1
2 is supported by a head arm 7,
The arm 7 is rotated by the actuator 3 in the direction of arrow b.
Then, the head 2 is moved to the target track of the recording medium 1.
Further, the fine movement actuator 4 corresponding to the head 2 moves the arrow a direction.
Each head 2 is finely adjusted.

The recording medium 1 has at least a data zone.
Sector servo method in which 5 and servo zones 6 are alternately formed
Or a part of the recording surface as a servo surface
And for the data zone 5 and the servo zone 6,
Because it is formed shifted in the circumferential direction corresponding to the head 2
And sequentially from a plurality of heads 2 according to the rotation of the recording medium 1.
The servo information of the servo zone 6 can be read.

The sequentially read servo information is switched to provide
To a plurality of heads 2
The servo demodulation circuit demodulates the servo information
Difference information can be determined. Also by control processing circuit etc.
With the configuration, the actuator 3 is driven based on the error information.
To control the positioning of the head 2 on the target track.
Error information based on servo information corresponding to
The fine movement of the head 2 according to the error information.
By driving the actuator 4, the position error between the heads 2 can be reduced.
Position compensation control for compensation can be performed.

In addition, one of a plurality of heads is used to transmit servo information.
The head to be read out is used for positioning control.
This is the reference head. And the other heads
Fine movement according to the error information obtained from the corresponding servo information.
Positioning compensation control by driving actuator 4
It can be performed.

When a target track is designated, the actuator is actuated.
The eta 3 moves the head 2 at a high speed near the target track.
Driven by the moving access mode, near the target track
When you reach the side, you will be positioned at the target track at low speed
Driven in the fine mode. On this target track
After positioning, the track following the target track
It is driven by the locking mode.

In the access mode in that case, the fine mode
Based on the servo information corresponding to the head
According to the error information, the fine movement
Drives the tutor 4 and performs positioning control in advance.
Speeding up access to the recording medium 1
Can be planned.

From the fine mode to the tracking mode
At the same time as the head that reads only servo information
Writing the data to the data zone or
Read and read servo information from servo zone
A difference value from the head position error is obtained. That is, depending on the temperature
Relative position between multiple heads due to differences in expansion and contraction
When a positioning error occurs, the relative position error must be detected.
And the relative position error is calculated by
It can drive and perform positioning compensation control.

[0017]

FIG . 2 is an explanatory view of an embodiment of the present invention.
The main part of the servo system when applied to the disk device is shown,
11-1 to 11-3 are magnetic disks as recording media;
12-1 to 12-3 are heads, 13 is an actuator,
14-1 to 14-3 are fine movement actuators, 15-1 to
15-3 is a data zone, 16-1 to 16-3 are servos
Zone, 17-1 to 17-3 are head arms, and 18 is
Pindle, 21 is a head switching circuit, 22 is a servo demodulation circuit.
23, a control processing circuit, 24, a driver switching circuit, 2
5 is a driver, 26 is a drive circuit of the actuator.
You.

In this embodiment, three magnetic disks 11-
Heads 12-1 to 12-3 are arranged on one side of 1-11-3
Each of the heads 12-1 to 12-3 has a head.
Arm 17-1 to 17-3.
Fine movement actuator 14-1 using strain element, magnetostriction element, etc.
14-3 allows fine adjustment of the track
It has a configuration. Also, each head arm 17-1
17-3 is rotated by the actuator 13 and
The heads 12-1 to 12-3 at the tip of the magnetic disk 11
-1 to 11-3.
You.

Each of the magnetic disks 11-1 to 11-3
The rack has data zones 15-1 to 15-3 and servo
Sectors 16-1 to 16-3 are alternately formed.
The head 12-1 to 1-1.
2-3, in this case, the magnetic disks 11-1 to 11-11
-3, the positions of the servo zones 16-1 to 16-3 are circled.
It is shifted in the circumferential direction.

Therefore, the head arms 17-1 to 17-3
The heads 12-1 to 12-2 at the tip of
Even if they are at the same position in the radial direction with respect to
The relative positions of the disks 11-1 to 11-3 on the tracks are different.
Will be. For example, the servo is controlled by the head 12-1.
After reading the servo information from zone 16-1, the magnetic data
The head 12 is moved according to the rotation of the disks 11-1 to 11-3.
Read servo information from servo zone 16-2 by -2
Then, the servo zone 16-3 is moved by the head 12-3.
The reading of the servo information from is repeated.

The head switching circuit 21 includes heads 12-1 to 12-1.
12-3 is for sequentially switching the servo information read from the servo zones 16-1 to 16-3 and adding the servo information to the servo demodulation circuit 22, and one servo less than the number of heads 12-1 to 12-3. The demodulation circuit 22 can demodulate the servo information. The servo information demodulated by the servo demodulation circuit 22 is applied to a control processing circuit 23, and a drive control signal is calculated in accordance with the difference between the instructed target track position and the current track position. Can be The actuator drive circuit 26 drives the actuator 13 according to the drive control signal to position the heads 12-1 to 12-3 on the target tracks. Note that, in FIG.
A head switching circuit, a data writing circuit, a data reading circuit, and the like for writing or reading data by -1 to 12-3 are not shown.

Fine movement actuators 14-1 to 14-3
Are provided between the head side of the head arms 17-1 to 17-3 and the actuator 13 side. Each of the fine movement actuators 14-1 to 14-3 includes two left and right electrostrictive elements, magnetostrictive elements, and the like. The case of a fine movement element is shown. By applying a control signal such that one of the left and right fine movement elements expands and the other contracts, the positions of the heads 12-1 to 12-3 with respect to the target track can be finely adjusted in either the left or right direction. it can. Note that a configuration in which fine adjustment is performed using one fine movement element is also possible.

When the head 12-1 of the heads 12-1 to 12-3 is positioned on the target track with reference to the head 12-1, for example, the other head 12-1
The relative positions of the actuators 13 and the head arms 17-1 to 17-17 due to differences in the internal temperature distribution and the like
The displacement may be caused by a small displacement of -3. In such a case, the data zone 15-1 is set by the head 12-1.
When reading data from the data zone 15-2 by switching to the head 12-2, the head 12-2 is displaced from the target track. Servo zone 16-
A fine movement control signal is formed by the control processing circuit 23 using the servo information from the servo control unit 2, and a fine movement control signal is added by switching to the driver 25 corresponding to the head 12-2 by the driver switching circuit 24.
4-2 can be driven, thereby accurately positioning the target track. That is, the positional deviation of the head that writes or reads data with respect to the head serving as the positioning reference can be corrected by controlling the fine movement actuator.

The above-mentioned reference head 12-1 can be a head for reading out only servo information. That is,
By reading the servo information from the servo zone 16-1, the positioning to the target track can be performed. Also, a magnetic disk having a servo surface is provided, the servo surface servo system is combined with the above-described sector servo system, and a servo head for reading servo information from the servo surface is used as the above-mentioned positioning reference head, and is compatible with the sector servo system. The fine movement actuator can be driven according to the position error based on the servo information read by the head to correct the position error.

The head serving as a reference for positioning may have a configuration in which the fine movement actuator is omitted, or a configuration in which the fine movement actuator is not driven when the fine movement actuator is provided. That is, the position error of the other head with respect to the reference head is corrected by the fine movement actuator.

FIG. 3 is an explanatory view of track development according to the embodiment of the present invention, showing a case where 15 heads 12-1 to 12-15 are positioned on tracks T1m to T15m by an actuator 13, and each head 12-1 is shown. ~ 12-15
Fine actuator 14-1 to fine-tune the position error
14-15 are provided. In addition, each track T1m to T
In the area 15m, data zones 15-1 to 15-15 and servo zones 16-1 to 16-15 are alternately arranged in the circumferential direction, but the servo zones 16-1 to 12-15 correspond to the heads 12-1 to 12-15. 1-16-15 are offset in the circumferential direction.

For example, data zones 15-1 to 15-1
5 and servo zones 16-1 to 16-15 are each 1
When 32 are formed in the circumference, the servo zones 16-1 to 16-1
6-15, the width and the period, and the circumferential displacement
When represented by relative time widths t1, t2, and t3 with respect to 2-1 to 12-15, for example, t1 = 10 μs and t2 = 347.2 μ.
s and t3 = 23.147 μs. That is, 5208μ
s indicates the time width when the magnetic disk makes one rotation.

The heads 12-1 to 12-15 are positioned at target tracks T1m to T15m, and all the heads 12-1 to 12-15 are positioned.
To stably correct the position of 12-15, each head 12-
According to 1 to 12-15, it is necessary to read servo information from about three servo zones. Therefore, the time required for position correction is t3 × 3 × (the number of heads) =
23.147 × 3 × 15 = 1041.615 (μs), which is about 1 ms, but there is no problem because the access time by the actuator 13 is about 10 to 20 ms, which is sufficiently shorter than this.

As described above, the 15 heads 12-1 to 12-1
By using both surfaces of the magnetic disk on which the tracks T1m to T15m corresponding to 12-15 are formed, only eight disks are required, and one surface can be a servo surface.
That is, as described above, by combining the servo surface servo method and the sector servo method, it is possible to perform positioning on the target track by the servo surface servo method and to correct the position error of each head by the sector servo method.

FIG. 4 is an explanatory diagram of the position error. The difference between the target track position and the current position of the head is a position error. The access mode moves to the vicinity of the target track, and the fine mode moves to the target track. And a tracking mode for following the target track. For example, as shown by the curve a, the robot is moved at a high speed in the access mode, the position error becomes substantially zero, and the mode shifts to the fine mode. However, hunting occurs when the target track is exceeded. Further, as shown by the curve b, when the movement is made at a low speed in the access mode, it is possible to shift to the tracking mode with almost no hunting when shifting to the fine mode. However, the control shown by the curve b has a disadvantage that the access time is longer than the control shown by the curve a. Therefore, the control shown by the curve a that enables high-speed access is adopted.

For example, if the positioning error of another head, that is, the data head, is corrected by the fine movement actuator immediately after shifting from the access mode to the fine mode based on the servo head when the servo surface servo system is combined, the target When the positioning of the servo head with respect to the track is stabilized, a positioning error of the data head will occur. Thus, as shown by the curve c, the data head is corrected by the fine movement actuator immediately after shifting from the access mode to the fine mode in anticipation of the positioning error of the transient response of the servo system. Therefore, the curve a
As in the case of the control shown in (1), a positioning error occurs due to the transient response.
Since the position error of the data head with respect to the servo head is corrected, the positioning error of each data head can be corrected almost completely without increasing the access time.

FIG. 5 is a block diagram of a main part of another embodiment of the present invention, and shows a control system for a fine actuator when a servo surface servo system and a sector servo system are combined. In the figure, 31-0 is a servo head, 31-1 to 31-15 are data heads, 32 is a head switching circuit, 33 and 34 are servo demodulation processing circuits, 35 is a switch circuit, 36 is an adder, 37 Is a driver control switching circuit, and 38-1 to 38-15 are drivers.

In this embodiment, one servo head 31-
0 and 15 data heads 31-1 to 31-15. The data heads 31-1 to 31-15 are provided with fine movement actuators (not shown).
38-15. The switch circuit 35 is turned on by a mode signal in the fine mode. The servo demodulation processing circuit 33 demodulates servo information read from the servo surface by the servo head 31-0 and outputs a position error signal.
The servo demodulation circuit 34 demodulates the servo information read from the servo zone by the data heads 31-1 to 31-15 switched by the head switching circuit 32, and outputs a position error corresponding to the data heads 31-1 to 31-15. It outputs a signal. The servo head 31-0 and the data heads 31-1 to 31-15 are positioned by an actuator (not shown). In this case, positioning control is performed based on servo information from the servo head 31-0. Will be

The switching between the head switching circuit 32 and the driver control switching circuit 37 is controlled synchronously. When the mode is shifted to the fine mode, the switching circuit 35 including transistors and the like is turned on by the mode signal, A position error signal from the servo head 31-0,
The adder 36 obtains a difference value between the selected and switched data heads 31-1 to 31-15 and the position error signal, and the driver control switching circuit 37 outputs the fine movement control signal corresponding to the difference value to the data head corresponding to the data head. Of the fine movement actuator.

Therefore, even in the process including the positioning error due to the transient response of the servo system, the relative position error between the servo head 31-0 and the data heads 31-1 to 31-15 can be corrected by the fine movement actuator. Therefore, when the servo head 31-0 is positioned on the target track and stabilized, the data heads 31-1 to 31-31 are stabilized.
The positioning error of -15 is corrected to be almost zero.

In each of the above-described embodiments, the recording medium is not limited to a magnetic disk, but can be applied to various types of recording devices such as an optical disk. , Can also be provided near the head. When the number of heads is large, the heads are divided into a plurality of groups, and a head switching circuit and a servo demodulation circuit are provided for each group. In addition, the present invention is not limited to the above-described embodiment, but can be variously added and changed.

[0037]

As described above, according to the present invention, the data zones 5 and the servo zones 6 are alternately formed in the circumferential direction, and the servo zones 6 are shifted in the circumferential direction corresponding to the head 2. Therefore, when the head 2 is switched, it is possible to read out predetermined servo information in a short time and control to follow the target track. Therefore, the relative positioning error of the head due to thermal off-track or the like can be reduced, and the signal margin for the off-track required in the conventional example can be eliminated. There is an advantage that the storage capacity can be greatly increased.

[0038]

As described above, according to the present invention, the data zone 5 and the servo zone 6 are alternately formed in the circumferential direction, and the position of the servo zone 6 is shifted in the circumferential direction corresponding to the head 2. has a recording medium 1 of the formed structure at least, f the reading head 2 the servo information of the servo zone 6
A servo demodulation circuit 22 ( see FIG. 2) for sequentially switching and inputting servo information by a head switching circuit 21 (see FIG. 2);
The actuator 4 is driven according to the error information from the servo demodulation circuit to control the positioning of the head 2, and the error information from the servo demodulation circuit 22 is transmitted to the driver switching circuit.
24 (see FIG. 2) , and the driver 25 of the fine movement actuator 4 (see FIG. 2) according to the error information corresponding to the head 2 .
2) , and has a configuration of a control processing circuit 23 (see FIG. 2) for performing positioning compensation control by driving the servo demodulation circuit for the plurality of heads 2 in a time-division manner. Since positioning control is performed, a conventional example in which a servo demodulation circuit is provided for a plurality of heads 2 or
Compared to a conventional example in which a plurality of heads 2 are grouped and a servo demodulation circuit is provided for each group, for example, one servo demodulation circuit can be used. Therefore, economy can be achieved. Furthermore, since error information corresponding to a plurality of heads 2 can be obtained, it is possible to drive the driver 25 of the fine movement actuator 4 according to the error information to perform positioning compensation control. Therefore, there is an advantage that the recording density can be increased, the storage capacity can be greatly increased, and high-speed positioning control can be performed.

In addition, one of the plurality of heads is
Servo information in the servo surface servo method and sector servo method
Is used as a positioning reference to read out the information and perform positioning control
Head and is displaced in the circumferential direction described above with respect to this head.
Other heads that read the servo information of the servo zone
Fine movement actuator based on error information corresponding to each head
By performing positioning compensation control by driving the
Can be corrected including the relative position error of several heads
There are advantages.

The mode is shifted from the access mode to the fine mode.
When moving the fine movement actuator 4
By driving according to the information, advanced positioning system
Control and high-speed and high-precision positioning control
There are advantages. Also, read the servo information and
Difference between the position error of the quasi-head and the position errors of other heads
The fine movement actuator 4 is driven with the minute as the relative position error.
To compensate for relative position errors and switch heads.
Writes or reads data from other tracks at high speed
There is an advantage that can be made.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of track development according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a position error.

FIG. 5 is a main part block diagram of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording medium 2 Head 3 Actuator 4 Fine movement actuator 5 Data zone 6 Servo zone 7 Head arm 8 Spindle

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Imamura 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-2-236875 (JP, A) JP-A-3-102684 (JP, A) JP-A-2-254686 (JP, A) JP-A-3-108166 (JP, A) JP-A-3-183070 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) G11B 21/08 G11B 21/10

Claims (3)

(57) [Claims] A plurality of recording media rotatably supported;
A head for writing data to or reading data from the plurality of recording media, an actuator for moving the head to a target track of the recording medium, and a fine movement actuator corresponding to the head; In a servo control method of reading recorded servo information by the head and positioning the head on a target track, the recording medium forms a data zone and a servo zone alternately at least in a circumferential direction, and The head has a configuration in which the position of the servo zone is shifted in the circumferential direction corresponding to the head, and the head for reading the servo information of the servo zone is sequentially arranged.
A head switching circuit for switching next and the head sequentially switched by the head switching circuit
A servo demodulation circuit for inputting the read servo information; driving the actuator in accordance with error information from the servo demodulation circuit to perform positioning control of the head;
A driver switching circuit that performs switching control synchronously with a switching circuit to drive a driver of the fine movement actuator corresponding to the head to perform positioning compensation control. 2. The head according to claim 1, wherein said head is an access mode and a fine mode.
Follow the target track of the recording medium through the mode
In the process of shifting to the tracking mode, the access
When shifting from fine mode to fine mode.
The driver of the micro-actuator corresponding to the head
Driver switching circuit that performs switching control synchronously with the driver switching circuit
Switch to drive according to the error information corresponding to the head.
2. The servo control system according to claim 1, wherein the servo control system comprises: 3. When the mode shifts to the tracking mode,
Position error of the head to read the servo information at
Write or read data from the
Position error corresponding to head that reads servo information from bozone
The fine movement actuator corresponding to the head
The driver of the printer is switched synchronously with the head switching circuit.
Switching compensation by driver switching circuit
3. An apparatus according to claim 1, further comprising a control unit.
The servo control method described.