JP2002093083A - Magnetic disk drive and servo control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize constitution wherein the center of rotation of a disk and the center of a data track nearly meet each other even if the center of a servo track on the disk and the center of rotation of the disk having eccentricity. SOLUTION: In the disk drive, a disk 1 having servo tracks previously constituted is built and a CPU 14 refers to an offset table 15A stored in a memory 15 when entering track tracking control by moving a head 2 to a target servo track. The CPU 14 performs position adjustment including compensation processing using offset values by servo sectors to position the head 2 in a range of data tracks having a concentric center almost meeting the center of rotation of the disk 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a magnetic disk drive such as a hard disk drive, and more particularly to a magnetic disk drive having a compensation function for compensating for the eccentricity between the center of a servo track recorded in advance and the center of rotation of the disk. About.

[0002]

2. Description of the Related Art In recent years, hard disk drives (hereinafter simply referred to as "disk drives") have been developed for a wide range of uses such as data storage devices of various digital devices such as mobile information devices as well as data storage devices of personal computers. It is getting. For this reason, there is an increasing demand for disk drives, in particular, for miniaturization, large capacity, and efficient manufacturing processes.

[0003] The manufacturing process of a disk drive includes a servo write process for recording (pre-recording) a servo track on a disk as a recording medium.
A servo track is composed of servo sectors in which servo data necessary for controlling the positioning of a magnetic head (hereinafter simply referred to as a head) at a target position on a disk is recorded. The servo data is recorded in a plurality of servo areas arranged at predetermined intervals in the circumferential direction. The area including this servo area up to and including the next servo area in the circumferential direction is called a servo sector.

[0004] On the other hand, a data track is formed as an area for recording user data based on the servo track. A data track is composed of a plurality of data sectors belonging to each servo sector (a data area serving as an access unit).
Consists of That is, each servo sector is identified by a sector number and serves as a reference for identifying each data sector. However, physically, a plurality of data sectors belonging to a servo sector are arranged not only between servo areas but also by a servo area included in the next servo sector.

[0005] To increase the capacity of a disk (to increase the recording density),
It depends on the positioning accuracy of the head. The positioning accuracy of the head depends on the recording accuracy of the servo track on the disk. Further, in order to improve the efficiency of the manufacturing process, it is also important to increase the efficiency of the servo write process. Therefore, in recent years, there has been proposed a method of recording a servo track on a disk by a dedicated device before assembling the disk in a disk drive. On the other hand, conventionally, a method of incorporating a disk into a disk drive and recording servo data on the disk has been generally adopted.

With the method of recording servo tracks on the drive body, it is possible to form a large number of accurate concentric servo tracks on a disk by a dedicated device and to efficiently execute a servo write process on a large number of disks. Becomes

In a disk drive manufacturing process, a disk on which servo tracks (ie, servo data) are recorded in a servo write process is incorporated into a drive body. Specifically, it is attached to a spindle motor which is a rotating mechanism of the disk. In such a manufacturing process, servo tracks can be accurately recorded on a disk in advance, and the efficiency of the manufacturing process can be improved.

[0008]

In a manufacturing method in which a disk in which servo tracks are formed in advance is incorporated in a disk drive, the efficiency of the servo write process can be improved. However, the following problem occurs.

That is, in the method of mounting the disk on the rotation shaft of the spindle motor and incorporating the disk into the drive, the center of each concentric servo track previously formed on the disk and the rotation center of the disk (the rotation shaft of the spindle motor) Does not always match (occurrence of eccentricity). When this state occurs, eccentricity occurs between the data track and the servo track, assuming a concentric data track based on the rotation center of the disk. In practice, since the data track is formed based on the servo sectors forming the servo track, eccentricity occurs between the center of rotation of the disk and the center of the data track.

When such eccentricity occurs, the interval between servo sectors on the same data track fluctuates.
The data read / write operation is performed based on the intervals between servo sectors. For this reason, a gap area is provided between data sectors in anticipation of a change in the interval between servo sectors due to a rotation change of the spindle motor or the like. However, if there is a change in the interval between servo sectors due to the eccentricity, the gap area is increased. A need arises. However, the method of increasing the gap area is not effective because it reduces the data recording area on the disk and hinders an increase in capacity.

Therefore, an object of the present invention is to provide a disk drive manufactured by a method of incorporating a disk in which servo data is recorded in advance, when eccentricity occurs between the center of a servo track on the disk and the rotation center of the disk. However, the object is to realize reliable recording and reproduction of data on the data track by making the rotation center substantially coincide with the center of the data track.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a disk drive in which a disk on which servo data is recorded in advance is incorporated in the drive. On the disk, a large number of servo tracks composed of a plurality of servo sectors arranged concentrically with respect to the first rotation center and at predetermined intervals in the circumferential direction are formed. The first center of rotation is the center of rotation of the disk when recording servo data on the disk.

The disk incorporated in the drive is rotated by a spindle motor with reference to the second rotation center. The second rotation center corresponds to the center of the rotation axis of the spindle motor. An eccentricity depending on the mechanical accuracy of the spindle motor exists between the rotation center of the disk which is the second rotation center and the first rotation center which is the center of the servo track. According to the amount of eccentricity, an offset value generated for each servo sector can be measured between a servo track and a data track assuming concentric circles based on the center of rotation of the disk. This offset value is determined by the rotation center of the disk and the center of the servo track.
Corresponds to the amount of misalignment corresponding to the amount of eccentricity with respect to the rotation center.

The servo system (servo control means) of the present invention performs position adjustment using the offset value when positioning the head on a target data track based on servo data read from a servo sector on the disk by the head. Execute. That is, the servo system compensates for the eccentricity between the center of the servo track and the center of rotation of the disk, and positions the head in a range of the data track having a concentric center substantially coinciding with the center of rotation of the disk.

More specifically, the disk drive of the present invention uses an offset setting means for setting an offset value for each servo sector and an offset value set according to the position of the servo sector corresponding to the target data track. Servo control means for controlling the position of the head within the range of the target data track. The offset setting means has, for example, a table means for storing an offset value measured in advance for each servo sector. The servo control means refers to the table means,
Find the offset value corresponding to the servo sector. In addition,
The offset setting unit may be a unit (a function of a CPU) that calculates an offset value for each servo sector by a calculation process according to the amount of eccentricity and the phase.

With a disk drive having such a configuration, when a data track is formed in accordance with a servo track previously formed on a disk, the eccentricity between the concentric center of the data track and the rotation center of the disk is suppressed. Thus, the respective centers can be substantially matched. Therefore, as a result, it is possible to realize high-precision positioning control of the head with respect to the data track, and to realize reliable recording and reproduction of data with respect to the data track. In other words, a manufacturing method in which a disk in which servo data is recorded in advance is incorporated in a disk drive can be adopted, so that a dedicated device can achieve high precision of a servo track formed on the disk. Further, since the recording processing of the servo tracks can be efficiently executed on a large number of disks, the efficiency of the servo writing process can be improved.

[0017]

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

(Structure of Disk Drive) As shown in FIG. 2, the disk drive according to the embodiment has a hard disk in which a disk 1 and a drive mechanism including a head actuator are incorporated in a housing 7 which is a drive body. Assume a drive. The head actuator includes an arm 4 on which the head 2 is mounted, a voice coil motor (VCM) 5, and a pivot shaft 6 for rotating the arm 4.

The head actuator is a CPU which will be described later.
The servo control of 14 controls the movement of the disk 1 in the radial direction to position the head 2 at the target position (target data track). Specifically, the arm 4 is driven around the pivot shaft 6 by the driving force of the VCM 5 to move the head 2 in the radial direction of the disk 1.

Before the disk 1 is mounted on the spindle motor 3 of the drive, servo data is recorded in advance by a dedicated device. The servo data roughly includes a track code (cylinder number), servo burst data, and a servo sector number. The track code is a track address for identifying a servo track (data track). The servo burst data is position error data used for track following control for positioning the head 2 within a servo track (data track). The servo sector number is a sector address for identifying a servo sector (data sector).

As shown in FIG. 1, the servo data is recorded in servo areas 101 arranged at predetermined intervals in the circumferential direction of the disk 1. The servo area 101 is a reference area that defines a servo sector including a plurality of data sectors. Each of the servo sectors constitutes a servo track 100 developed in the circumferential direction. Servo track 1
The reference numeral 00 denotes a concentric circle with respect to a disk rotation center (first rotation center) 400 when servo data is recorded.

The disk 1 is mounted on a spindle motor 3 of a drive, and is rotated at a high speed by the spindle motor 3 during a data read / write operation. In this case, the rotation center of the disk (the spindle motor 3) is influenced by the mechanical accuracy such as the outer diameter of the hub of the spindle motor 3.
Axis of rotation) 300 and the center of rotation 400 of the servo track
Between them, an eccentricity of about several tens of μm occurs.

FIG. 3 is a block diagram showing a read / write signal processing circuit and a control system of the disk drive.

The read / write signal processing circuit comprises a preamplifier circuit 10 and a read / write channel 11.
The preamplifier circuit 10 has a read amplifier that amplifies a read signal read by the head 2 and a write amplifier that converts write data into a write current. The read / write channel 11 performs various signal processing such as A / D conversion processing, write data encoding processing, and read data decoding processing. Disk controller (HDC) 1
Reference numeral 2 denotes an interface between the drive and a host system (a personal computer or a digital device), and executes read / write data transfer control and the like.

The control system is roughly divided into a motor driver 13 and a microprocessor (CPU) 14. The motor driver 13 includes a VCM driver 13A for driving the VCM 5 and a spindle motor (SP).
M) 3) to drive the SPM driver 13B. The CPU 14 is a main control device of the drive,
This is a main element of a servo system for executing positioning control of the head 2. The CPU 14 operates according to the servo data reproduced by the read / write channel 11,
The control of the seek operation and the track following control are executed. C
The PU 14 is an input value (voltage value) of the VCM driver 13A.
To control the driving of the head actuator. The memory 15 includes a RAM and a flash EEPROM.
OM, and stores a control program of the CPU 14 and an offset table 15A related to the embodiment.

The offset table 15A includes an offset value corresponding to the amount of eccentricity generated between the rotation center 300 of the disk and the rotation center 400 of the servo track. The eccentricity is measured during the manufacturing process of the disk drive. The offset value is, as will be described later, between the rotation center 300 of the disk and the concentric data track 2.
This is a position adjustment value for substantially matching the center of 00. Here, the eccentricity is measured for each position of each servo sector configuring the servo track 100. The offset table 15A stores an offset value calculated for each servo sector according to the amount of eccentricity.

Here, the measuring method of the eccentric amount is as follows.
The CPU 14 moves the head 2 to a predetermined servo track 100
Track following control for positioning to the position. At this time, at least one round of position error data is taken from the servo track 100. The position error data is data indicating a position error value (position error value with respect to the track center line) calculated from servo burst data used when performing positioning control of the head 2 within the track range.
The CPU 14 estimates the amount of eccentricity from the obtained fluctuation value of the position error data and the characteristics of the head positioning control system. As another measuring method, the head 2 is fixed on a predetermined servo track 100 on the disk 1 while the head actuator is moved until it comes into contact with the inner peripheral side stopper or the outer peripheral side stopper. The CPU 14
In this state, a predetermined servo track 100 is
Fetches at least one round of servo data read out from the. The CPU 14 estimates the eccentricity from the fluctuation value of the obtained servo data.

(Servo Control Operation) The operation of the disk drive including the servo control operation (head positioning control operation) will be described below with reference to FIGS. 1 to 3 and the flowchart of FIG.

When the target data track to be accessed is set, the CPU 14 executes a seek operation for moving the head 2 to a servo track corresponding to the target data track (steps S1 and S2). In the seek operation, the CPU 14 detects the current position of the head 2 based on the track code read from the servo area by the head 2. The CPU 14 sets a speed value according to the moving distance between the current position of the head 2 and the target position, and controls the driving speed of the actuator so as to match the speed value.

When the head 2 moves to the servo track range corresponding to the target data track, the CPU 14 shifts to track following control (step S3). In the track following control, the CPU 14 calculates position error data from servo burst data read by the head 2,
The drive of the actuator is controlled so that the position error value becomes zero. That is, the CPU 14 executes the position control so that the head 2 is maintained within the range of the servo track corresponding to the target data track.

Here, the CPU 14 refers to the offset table 15A stored in the memory 15 and searches for an offset value corresponding to the sector number of the servo sector read by the head 2 (step S4). And
Using the acquired offset value, the CPU 14 adjusts the position of the head 2 set by the track following control (step S5). That is, the CPU 14 controls the position of the head 2 by executing a compensation process of adding an offset value for each servo sector to the position error value calculated by the track following control process.

In short, the CPU 14 executes position adjustment (eccentricity compensation) corresponding to the amount of eccentricity between the center 400 of the servo track 100 and the center 300 of rotation of the disk using the offset value. Accordingly, the position of the head 2 is adjusted within the track range compensated by the amount of eccentricity with respect to the range of the target servo track for each servo sector configuring the servo track 100. The track range whose position has been adjusted is a concentric target data track based on the rotation center 300 of the disk. Therefore, CP
U14 performs a data read / write operation on the specified data sector (specified according to the servo sector number) by the head 2 positioned in the range of the target data track (step S6).

As described above, according to this embodiment, the center 400 of the servo track 100 and the center of rotation 3 of the disk are
By executing the track following control of the head 2 using an offset value corresponding to the eccentricity with 00, the head 2 does not substantially coincide with the data track corresponding to the servo track 100 but with the rotation center 300 of the disk. It can be positioned in the range of the data track having the concentric center. Therefore, with the head 2 positioned,
By recording data in each data sector, the data track including the data sector is configured. In other words, the center 400 of the servo track 100 formed on the disk 1 and the rotation center 300 of the disk
Even if eccentricity occurs between the two, a data track having a concentric center substantially coincident with the rotation center 300 of the disk can be formed.

Therefore, the disk drive can always accurately position the head 2 on the target data track and reliably execute the data read / write operation for the specified data sector included in the target data track.
In other words, the disk 1 on which the servo tracks are formed in advance
Can be adopted in the disk drive, so that the efficiency of the disk drive manufacturing process can be promoted along with the efficiency of the servo write process. In addition, since servo tracks can be accurately and densely recorded on the disk 1 by a dedicated device, it is possible to realize a large capacity accompanying a high recording density of the disk.

In this embodiment, the offset value according to the amount of eccentricity is described as being set in the table 15A for each servo sector. However, the present invention is not limited to this. For example, the CPU 14 controls the memory 1 during the head positioning control.
5 may be used to calculate the offset value each time by using the eccentric amount stored in 5.

[0036]

As described above in detail, according to the present invention, in a disk drive manufactured by a method of incorporating a disk in which servo data is recorded in advance, the distance between the center of a servo track on the disk and the rotation center of the disk is determined. Even when eccentricity occurs, the positioning control of the head can be realized such that the rotation center and the concentric center of the data track substantially coincide with each other. Therefore, since the position of the data track can be stabilized with respect to the center of rotation of the disk, reliable recording and reproduction of data on the data track can be realized.
In other words, a manufacturing method in which a disk in which servo data is recorded in advance is incorporated in a disk drive can be adopted, so that a dedicated device can achieve high precision of a servo track formed on the disk. Further, since the recording processing of the servo tracks can be efficiently executed on a large number of disks, the efficiency of the servo writing process can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a disc according to an embodiment of the present invention.

FIG. 2 is an exemplary view showing a mechanism of the disk drive according to the embodiment;

FIG. 3 is a block diagram showing a signal processing circuit and a control system of the disk drive.

FIG. 4 is a flowchart for explaining the operation of the disk drive.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Disk 2 ... Head 3 ... Spindle motor (SPM) 4 ... Arm 5 ... Voice coil motor (VCM) 6 ... Pivot shaft 7 ... Housing 10 ... Preamplifier circuit 11 ... Read / write channel 12 ... Disk controller (HDC) 13 ... Motor driver 14 ... CPU 15 ... Memory 15A ... Offset table

Claims (6)

[Claims] 1. A magnetic head for recording and reproducing data, and a servo track comprising a plurality of servo sectors including a servo area on which servo data is recorded and formed concentrically with respect to a first rotation center. A disk having a data track formed concentrically with respect to a second rotation center different from the first rotation center; a spindle motor for rotating the disk about the second rotation center; Offset setting means for setting an offset value for each servo sector according to the amount of eccentricity between the first rotation center and the second rotation center; and the magnetic head according to the servo data when recording or reproducing data. Means for performing positioning control on a target data track on the disk, the control corresponding to the target data track And a servo control means for controlling the magnetic head to adjust its position within the range of the target data track using the offset value set according to the position of the servo sector. apparatus. 2. The apparatus according to claim 1, wherein the offset setting means includes table means for recording, for each of the servo sectors, an offset value corresponding to an eccentricity between the first rotation center and the second rotation center. The servo control means refers to the table means,
2. The magnetic disk drive according to claim 1, wherein an offset value corresponding to a position of a servo sector corresponding to the target data track is obtained. 3. A magnetic head for recording and reproducing data, a plurality of servo sectors on which servo data is recorded, and servo tracks formed concentrically with respect to a first rotation center; A disk having a data sector set between the disks and a disk having a data track concentrically formed with a second rotation center different from the first rotation center as a reference. Controlling the magnetic head to perform a seek operation to a target data track on the disk; and, when shifting from the seek operation to track following control, the first rotation center and the second rotation center. Setting an offset value for each of the servo sectors according to the amount of eccentricity with respect to the rotation center; Controlling the magnetic head to adjust the position within the range of the target data track using the offset value set according to the position of the corresponding servo sector. . 4. The method according to claim 1, wherein the setting step corresponds to an amount of displacement between the servo track and the data track in accordance with an eccentric amount between the first rotation center and the second rotation center for each of the servo sectors. 4. The servo control method according to claim 3, further comprising the steps of: referring to a table on which an offset value to be recorded is recorded; and determining an offset value corresponding to a position of a servo sector corresponding to the target data track. . 5. A magnetic disk drive for recording / reproducing data on / from a disk by a magnetic head, wherein the disk is formed concentrically with respect to a first rotation center on the disk, and controls the positioning of the magnetic head. A servo track composed of a plurality of servo sectors on which servo data for performing the servo data are recorded; and a data sector formed concentrically with respect to the second rotation center on the disk and set between the servo sectors. A data track, and wherein the first rotation center has an offset corresponding to a predetermined eccentricity with respect to the second rotation center which is a rotation center of the disk when recording and reproducing the data. A magnetic disk drive characterized in that: 6. The first rotation center corresponds to a rotation center of the disk set when forming the servo track on the disk, and the second rotation center is formed by the servo track. 6. The magnetic disk drive according to claim 5, wherein the disk corresponds to a rotation center when the disk is mounted on a rotation shaft of a spindle motor constituting a disk rotation mechanism.