JP3336819B2 - Magnetic disk drive and method of manufacturing the same - Google Patents

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 for positioning a head on a specific track by closed-loop control, and more particularly to recording and demodulation of a position signal (servo signal) for positioning, and more particularly, to recording and demodulation of a position signal after servo writing. The present invention relates to a head positioning control method suitable for obtaining a uniform track pitch by correcting waviness, and a servo writing method suitable for improving a writing position accuracy at the time of servo writing in a transfer method STW (servo track write) described later. .

[0002]

2. Description of the Related Art In a magnetic disk drive of closed loop control, a position signal for positioning a head at a specific track is, as shown in Japanese Patent Application Laid-Open No. 58-222468, an amplitude difference between a burst of an even track and a burst of an odd track. It is generally made from. The recording pattern of the position signal is called a servo pattern and is recorded by a servo track writer before product shipment, and is not rewritten after recording.

The position signal is a guide for positioning the head on a specific track, and it is essential that the position signal is accurately recorded in order to improve the track sealing of the magnetic disk.

A servo track writer is disclosed in
As disclosed in Japanese Patent No. 48276, a method in which the head feed function is dependent on a mechanism outside the HDD is disclosed.
As disclosed in Japanese Unexamined Patent Publication No. 777, a transfer method utilizing the mechanism of an HDD is known. Here, the transfer method means a position signal already recorded on a magnetic disk incorporated in an HDA (head disk assembly) (specifically, a first base pattern (corresponding to a track center interval along a radial direction of the disk). New servo patterns are recorded based on the second base pattern (recorded substantially continuously along the radial direction at each position corresponding to the sector position). Means the method of recording.

[0005]

With the recent increase in the density of magnetic disk drives, the track density has also been improved, and it is expected that the track density will soon reach that of an initial optical disk. In order to increase the track density, it is necessary to improve the track pitch accuracy, that is, to improve the position signal accuracy. However, due to fluctuations in the position of the reproduced signal due to the above, sufficient flatness of the position signal is not necessarily obtained.

As a result, the swell of the position signal (non-flatness)
, The head also moves, so that the track pitch varies.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for correcting a swell of a position signal after servo writing and preventing a change in track pitch. Another object of the present invention is to provide a method for improving the position accuracy of the position signal by improving the head position accuracy at the time of servo writing of the above-described transfer method STW. Note that the transfer method STW referred to herein is a method in which the head is positioned at a position signal (base pattern) already recorded on the disk incorporated in the HDA (head disk assembly), and a new position is set. It means a method of recording a signal (servo pattern).

[0008]

According to a first aspect of the present invention, a head positioning control method for a magnetic disk drive comprises a closed loop control system configured with a position error signal obtained based on a difference between a position signal and a head position. In a magnetic disk drive that calculates the amount of movement of the head and positions the head on a specific track, creates correction data for a rotation synchronization component of a position signal, records the correction data in a servo area of the disk, Is read out to correct the position error signal, and the head is positioned on a specific track by closed-loop control based on the corrected position error signal.

According to a second head position control method for a magnetic disk drive of the present invention, the head position control method for the first magnetic disk device is based on a following state in which a head is positioned on a specific track.
The position error signal Pos is measured, and the head movement amount X is calculated from the measured position error signal Pos and the loop transfer characteristic of the servo system and other related transfer characteristics, and further, Pos + X
And calculating the correction data in the specific track.

According to the servo write method for a magnetic disk drive of the present invention, when recording a servo pattern on a magnetic disk drive of a closed loop control, a head is targeted based on a position signal (base pattern) previously recorded on a specific disk surface. A servo write method for a magnetic disk drive that positions a track and records a new position signal (servo signal) on a target track. When performing head position control at the time of servo write, a rotation synchronization component of the position signal (base pattern) is determined. It is characterized by correction.

[0011]

According to the present invention, a position error signal Pos (a relative error between the position signal recorded on the disk and the head movement amount) that can be measured during the following operation of the head.
Calculates the amount of movement X of the head from the loop transfer characteristics of the servo system and other related transfer characteristics, calculates the swell Pos + X of the position signal caused by vibration during STW and the surface of the disk, and stores the calculation result in the servo area. Recorded as correction data. At the time of following, the correction data is reproduced and subtracted from the position error signal Pos to correct the head position in the following operation.

Further, in order to improve the signal quality of the STW of the transfer system, the undulation of the track followed by the head is calculated from a position error signal based on a position signal (base pattern), and is corrected using the result. The trajectory accuracy of the head during STW has been improved.

Therefore, according to the present invention, in a magnetic disk drive in which a head is positioned at a specific track by closed-loop control, even if a track (track) to be followed is waving, the swell of the track is corrected.
In effect, the position of the head can be controlled with the trajectory having no waviness as a target, and the track pitch accuracy of the HDD and the write position accuracy of the transfer STW can be improved.

[0014]

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

FIG. 1 is a block diagram of a servo system in an HDD to which the present invention is applied. In the block diagram shown in FIG. 1, 1 / S ² indicates a force and displacement transmission characteristic when the mechanism system is assumed to be an inertial system for simplification. M is the mass of the movable part, and K is a force coefficient indicating the relationship between current and force of a VCM (voice coil motor). G
(S) shows a transfer characteristic of a filter, a D / A converter, a power amplifier, and the like. The rotation synchronization error correction value is a value for correcting swell of rotation synchronization, and a detection method will be described later. The target position is a position signal Y (track information on the disk, recorded on the disk by the servo track writer, and a position error signal Pos when the head is fixed).
(Equivalent to that described later), and undulates due to undulation depending on the disk surface shape, vibration during servo writing, and the like. The undulation of the target position is known, and if the undulation is corrected (the rotation synchronization error signal value is added forward to the servo system (subtraction here)) as shown in FIG. 1, the movement of the head relative to the flat position signal is obtained. The quantity X is obtained and the head can be positioned with a flat position signal.

Next, a method of detecting a swell component at a target position and storing the data will be described. First, a method of detecting a waviness component, that is, a rotation synchronization error correction value will be described. In a conventional main magnetic disk drive, only a position error signal Pos, which is a difference between a movement amount X of the head and a position signal Y on the disk surface, can be detected in addition to the VCM current. Suppose now that the magnetic head is following a specific track. At the time of following, the ideal position signal Y indicating the target position is zero, but the position signal Y output at the time of following is actually a swell component. FIG.
As is apparent from the above, the relationship between the moving amount X of the head, the position error signal Pos, and the undulation component Y is expressed as Pos = Y−X. Therefore, in order to know the undulation Y of the target position (target track), the movement amount X of the head with respect to the inertial coordinate system is calculated from the measurable position error signal Pos, and Y =
Obtained from the calculation of Pos + X. Note that X is a value obtained by multiplying the position error signal Pos by a loop characteristic, as is apparent from FIG. This loop characteristic can be measured, and can be represented by a mathematical expression by modeling a controlled object. The transfer characteristic display is shown in the following equation.

[0017]

(Equation 1)

Further, since Pos includes vibration and electric noise at the time of following, an average of several rotations is taken to detect a rotation synchronous component, and a signal (<Po) is obtained by removing an asynchronous component.
s>). That is,

[0019]

(Equation 2)

Therefore, the correction data of the rotation synchronization is obtained by the following equation with respect to the data excluding the asynchronous component.

[0021]

(Equation 3)

The calculation of Y and <X> is performed in the time domain.

FIG. 2 is a conceptual diagram showing a relationship among a target position (Y (Tt)), a head position (X (t)), and a position error signal (Pos (t)).

Next, a description will be given of a method of storing the undulation of the target position (target track) obtained for each track by the above-mentioned method, that is, a rotation synchronization error correction value. Since the rotation synchronization error correction value (undulation) is obtained for each track, an extremely large storage capacity is required. Therefore, although it is possible to record the correction data on the semiconductor memory, the cost is increased. Therefore, the correction data is recorded on the track on the disk surface together with the corresponding position information. This correction data becomes the rotation synchronization error correction value in FIG.

FIG. 3 shows an example of a state in which correction data (rotational synchronization error correction value) is continuously recorded in a position information section on a magnetic disk in a magnetic disk drive of a sector servo system. The recording procedure and the like will be described in detail with reference to FIG.

In FIG. 3, M is a sector marker and a synchronization area, G is a gray code area, and P is a position signal area. These areas have the same form as the servo information area used in the conventional apparatus. The position of the servo area is detected by the sector marker, a reference signal for the gray code area G and the position signal area P is generated in the synchronous area, and the approximate position of the track is detected in the gray code area G. P detects high-resolution position information. In this embodiment, a two-phase servo pattern is written in the position signal area P. The swell of the position signal described above is a deviation of the position signal area P from an ideal position for each sector. In the present embodiment, the deviation for each sector is recorded as correction data for each corresponding sector. The corresponding sector may be the same sector or one sector before. The correction data is obtained by the method described with reference to FIG. 1 and then coded, and is detected by the same circuit that performs the gray code detection. Therefore, the correction data is recorded at the same clock as the gray code. This is the PLL
A (phase-locked loop) circuit generates a signal synchronized with the signal in the synchronization area of the servo information area, and records this signal as a clock or uses a clock at the time of servo writing. The correction data is coded, and an error check code called CRC or an error correction code called ECC is recorded together with the correction data in order to prevent erroneous detection.

Next, a circuit configuration for correcting a position error signal (rotation synchronization signal) at the time of following using the correction data will be described in detail with reference to FIG.

FIG. 4 is a block diagram showing an example of a schematic configuration of a control system of the HDA. In FIG. 4, the magnetization state of the disk 1 is detected by the head 2, amplified by the R / W (read / write) IC 10, and the output is made constant by the AGC (auto gain control) amplifier 11. Next, A
The output of the GC amplifier 11 is pulsed by the pulse generating circuit 12. Next, a marker detection / gate signal generation circuit (shown as “M detection gate generation” in the figure) 13 detects a sector marker, detects a sector start position, and outputs a gate signal in a gray code area, a correction data storage area, and the like. Occurs. Based on these gate signals, a clock synchronized with the recording signal is generated by the PLL circuit 15 and a gray code detection / correction data code detection circuit (“G detection C
The detection 14 detects the gray code, the correction data code and the check code. These data are stored in a DSP (Digital Signal Processor) 17
To form a closed loop for positioning the head together with the position error signal detected by the POS demodulation circuit 16. The DSP 17 obtains a control amount by subtracting a rotation synchronization error correction value (correction data) and a position error signal and performing arithmetic processing of a digital filter, and moves the VCM 3 (voice coil motor) via the power amplifier 18. At this time, the correction data is corrected by the DSP 17 by the above-described method so as to remove the component synchronized with the rotation. Correction data C
RC processing and ECC processing are also performed inside the DSP 17. If the correction data is found to be erroneously detected by the CRC processing and the ECC processing, the data is not used.

As described above, the correction data is used for correcting the position signal. As a result of correcting the position signal, the position error signal indicates the movement of the head more accurately, and the position of the head is corrected. The effect is also great for checking. Note that the correction operation need not be performed for all tracks, but can be performed only for specific tracks having large undulations.

The example shown in FIG. 3 is a case where the recording head and the reproducing head are the same, but an MR (magnetoresistive) head is employed as the reproducing head, and the recording head and the reproducing head are combined. Heads are being developed. In such a composite head in which the recording and reproducing heads are separated,
When recording and reproducing on the same track, the head position may be different between recording and reproduction. As a countermeasure in this case,
Priority is given to accurately positioning the head position during recording. Therefore, as shown in FIG. 5, the correction data W is recorded by providing a correction data storage area C at the P position of the reproducing head 2b during recording. FIG. 5 shows the positions of the recording head 2a and the reproducing head 2b. Therefore, in order to record the correction data W, the recording head 2 is made to be readable by the reproducing head 2b.
a is offset and recorded.

In order to record correction data for both recording and reproduction, correction data W for recording and correction data R for reproduction are provided, respectively. FIG. 6 is a diagram showing an example in which correction data W for recording and correction data R for reproduction are provided. In this correction, it is also possible to correct only a position on the disk surface where the waviness is particularly large.

The present invention can be applied to a case where a new position signal (servo signal) is recorded on a disk surface of a magnetic disk drive by a transfer method. In this case, the head is positioned based on a position signal (base pattern) previously recorded on a specific disk surface by closed loop control, and at that time, correction data of a rotation synchronization component of the position signal is created, and the correction is performed. The position error signal is corrected using the data, the head is positioned on the target track by closed loop control based on the corrected position error signal, and a new position signal (servo signal) is recorded. Thereby, the transfer mold S
TW writing position accuracy can be improved.

The servo system in this case is the same as in FIG. 1, but the correction error does not need to be recorded on the disk. That is, the undulation of the track is calculated at the position to be recorded, and then the servo pattern is recorded while correcting using the data. After moving to the next track, the swell of the track is newly calculated, and the above operation is repeated.

In the case of the transfer method, the eccentricity component among the rotation synchronous components may be very large. Therefore, the eccentricity is determined in advance, and the eccentricity is determined by the feed word when the correction data is determined. It may be possible to make a correction. When recording a position signal (servo signal) by transfer, correction is performed by adding correction data newly obtained to the eccentricity of the feedforward.

The present embodiment shows the concept of the present invention, and is not limited to a format, a hardware configuration, or the like.

According to the above embodiment, even when the track to be followed in the closed loop control disk device is wavy, the undulation of the trajectory can be corrected, so that the track pitch accuracy can be improved. Further, in the transfer type STW device, the position accuracy of a new servo pattern can be improved by correcting the undulation of the following position signal during recording. Further, by correcting the undulation of the trajectory, the position error signal accurately indicates the movement of the head, and it is possible to set the write protection or the like more accurately.

[0037]

According to the present invention, even in the case of a trajectory to be followed in a servo system that performs closed loop control, the undulation of the trajectory can be corrected. As a result, the position of the head can be controlled with the trajectory having no waviness as a target, and the track pitch accuracy of the HDD and the writing position accuracy of the transfer STW can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a servo system in an HDD to which the present invention is applied.

FIG. 2 is a conceptual diagram showing a relationship among a target position, a head position, and a position error signal shown in FIG.

FIG. 3 is a diagram illustrating an example of a state in which correction data (rotational synchronization error correction value) is continuously recorded in a position information section on a magnetic disk in a magnetic disk device of a sector servo system.

FIG. 4 is a block diagram showing an example of a schematic configuration of an HDA control system to which the present invention is applied.

FIG. 5 is an explanatory diagram showing an example of a method of storing correction data.

FIG. 6 is an explanatory diagram showing an example of a method of storing correction data.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disc, 2 ... Head, 2a ... Recording head, 2b ...
Reproduction head, 3 VCM, 4 carriage, 10 R /
W (read / write) ICs 10, 11 ... AGC (auto gain control) amplifier, 12 ... pulsing circuit, 1
3 ... Marker detection / gate signal generation circuit (shown as "M detection gate generation" in the figure), 14 ... Gray code detection / correction data code detection circuit (shown as "G detection C detection" in the figure), 15 ... PLL circuit, 16 POS demodulation circuit, 17
... DSPs (Digital Signal Processors) 17, 18 ...
Power amplifier (shown as PA in the figure).

Continuation of the front page (56) References JP-A-7-5076 (JP, A) JP-A-4-321983 (JP, A) JP-A-63-114465 (JP, U) (58) Fields investigated (Int) .Cl. ⁷ , DB name) G11B 21/08-21/10 G11B 5/56-5/60

Claims (6)

(57) [Claims] A closed loop control system comprising a position error signal obtained based on a difference between a position signal and a head position as a component .
A function of creating correction data of a rotation synchronization component of a position signal for a plurality of tracks in a magnetic disk device that positions a head on a specific track by control; a function of recording the correction data in a servo area of a disk; Function to read out the correction data recorded in the servo area and correct the position error signal
When the magnetic disk apparatus, wherein <br/> has a function to position the head by a closed loop control have groups Dzu the corrected position error signal to a particular track. 2. A position error signal Pos is measured in a following state in which a head is positioned on a specific track.
A function for calculating the amount of movement X of the head from the measured position error signal Pos, the loop transfer characteristic of the servo system, and other related transfer characteristics; and calculating Pos + X to obtain the correction data for the specific track. Have a function
2. The magnetic disk drive according to claim 1, wherein: 3. When a servo pattern is recorded on a magnetic disk device of closed loop control, a head is positioned on a target track based on a position signal (base pattern) previously recorded on a specific disk surface, and a new position signal (servo signal) is recorded. signal)
The method of manufacturing a magnetic disk device having a step of recording the target track, the step, when performing head position control in the servo writing to a plurality of tracks, corrects the rotation synchronization component of the position signal (base pattern) A method for manufacturing a magnetic disk drive, comprising a step of processing . 4. A disc on which a position signal is recorded, and
Magnetic disk having a head capable of reading a position signal
In the device Position signals are stored in servo areas of a plurality of tracks on the disk.
That the correction data of the rotation synchronization component of the signal is recorded
Characteristic magnetic disk drive. 5. A disc on which a position signal is recorded, and
Magnetic disk having a head capable of reading a position signal
In the device Position signals are recorded in servo areas of all tracks of the disk.
The feature is that the correction data of the rotation synchronization component is recorded
Magnetic disk device. 6. A magnetic disk drive according to claim 4, wherein:
At The position error signal during the following operation of the head and the
Based on the correction data read by the head
Computing processing means for calculating a control amount of the head; A void for performing a head positioning operation based on the control amount.
A coil motor, A magnetic disk drive comprising: