KR100734267B1 - MR offset measuring method of hard disk drive and recording medium for the same - Google Patents

Abstract

The present invention relates to an MR offset measurement method of a hard disk drive, and more particularly, to an MR offset measurement method for measuring an MR offset using a reference servo signal.

MR offset detection method of a hard disk drive according to the present invention

Recording the second servo patterns based on the first servo patterns recorded on the disc so as not to overlap the first servo pattern in the track direction;

Reading the first servo pattern while following a target track to which the MR offset is to be measured based on the second servo pattern; And

And measuring the MR offset by the difference between the center position of the target track and the position represented by the first servo pattern.

The MR offset detection method of the hard disk drive according to the present invention reads the reference servo pattern while following the track with reference to the final servo pattern, and calculates the MR offset using the position information indicated by the reference servo pattern. It has the effect that the MR offset can be measured.

Description

MR offset measuring method of hard disk drive and recording medium for the same}

1A and 1B show different magnetic recording heads, respectively.

FIG. 2 is for showing that the offset occurs in accordance with the position on the disc in the magnetic recording head shown in FIG. 1B.

3 shows the disks assembled in the hard disk drive.

4A and 4B are diagrams for schematically showing a self servo recording method.

5 is a schematic view of the MR offset measurement method according to the present invention.

6 is a flowchart illustrating an MR offset measuring method according to the present invention.

7 shows a configuration of a hard disk drive 10 to which the present invention is applied.

8 shows an electrical circuit of a hard disk drive to which the present invention is applied.

The present invention relates to a method for measuring MR offset of a hard disk drive, and more particularly, to a method of measuring MR offset using a final servo pattern and a reference servo pattern, and a recording medium storing a program suitable therefor.

The hard disk drive includes a plurality of magnetic heads coupled with rotating disks. The head records and reads information by magnetizing the disk surface and sensing the magnetic field. Magnetic heads have been developed that have a recording element for magnetizing the disc and a separate reading element for sensing the magnetic field of the disc. The readout element is typically composed of a magneto-resistive material. The magnetoresistive material has the property that the resistance changes in accordance with the magnetic field of the disk. A head having a magnetoresistive reading element is generally referred to as a magneto-resistive (MR) head.

Each head is attached to a bent arm made in a subassembly, commonly called a head gimbal assembly (HGA). The head gimbal assembly is attached to an actuator arm. The actuator arm has a voice coil motor that can move the head across the disk surface.

Information is typically stored in radiation tracks drawn across the surface of each disk. Each track is typically divided into segments. The voice coil motor and actuator arm make it possible to move the head to another track of the disk.

In order to accurately record and read data, it is desirable to keep the head in the center of the track. In order to be able to control the position of the head, each sector of the disc generally contains a number of servo burst signals which are located opposite the centerline of the track. The signals generated by the servo burst signals typically determine the position of the head relative to the track's centerline and generate a position error signal (PES) that is used to move the actuator arm when the head is not located on the track's centerline. .

In a hard disk drive, a head generally referred to as a magnetoresistive head is used, which has a read head composed of an inductive recording head and a magnetoresistive (MR) material. The recording head and the reading head are separated to some extent along the center line in the track direction and, in some cases, shifted in the radial direction of the disc. When the recording head and the reading head are arranged to be offset in the radial direction of the disc, there is an offset between the center of the recording head and the center of the reading head. Even if the recording head and the reading head are not shifted from each other in the radial direction of the disk, the center of the recording head and the center of the reading head are shifted from each other depending on the position of the actuator arm, that is, the position on the disk of the head.

The presence of an offset between the recording head and the reading head means that the position of the reading head must be corrected by the offset in reading the data read by the recording head into the reading head. Since the offset depends on the position of the head on the disk, the offset according to the position on the disk should be detected and stored for reference during the recording and reading operation.

If the MR offset is not detected correctly, it becomes difficult to accurately compensate the MR offset. This increases the bit error rate in read operations and increases the adjacent trackium in write operations.

1A and 1B show different magnetic recording heads, respectively. FIG. 1A shows a case where the center of the recording head is different from the center of the reading head, and FIG. 1B shows a case where the center of the recording head and the center of the reading head are the same. In the magnetic recording head shown in Fig. 1A, it can be seen that there is an offset between the center of the recording head and the center of the read head.

FIG. 2 is for showing that the offset occurs in accordance with the position on the disc in the magnetic recording head shown in FIG. 1B. The magnetic recording head is moved arcuately in the radial direction of the disc by the operation of the actuator arm. As a result, the center line of the magnetic recording head and the track center line on the disc do not coincide with each other. That is, skew and offset occur. Referring to Fig. 2, even when the read head is aligned with the track center line, it can be seen that the recording head is somewhat separated from the track center line, that is, the offset has occurred. The magnitude of this offset depends on the movement of the actuator arm, that is, the position of the magnetic recording head on the disc.

Conventionally, the MR offset is measured by a method of searching for an optimal head position for recording a specific burst or data and then reading it out. Specifically, after recording the servo burst having a specific frequency while following the centerline of the target track to be measured, the recorded servo is performed while performing micro jogging operation, that is, changing the off-track amount of the read head little by little. The position where the magnitude of the servo burst signal detected from the burst is maximized is searched. When the position where the magnitude of the servo burst signal is maximized is found, the distance from the center of the target track to the position where the magnitude of the servo burst signal is maximum is determined as the MR offset.

Alternatively, after the specific data is recorded while following the center line of the target track, the recorded data is read while the micro jogging operation is performed to search for a position where the number of error occurrences is minimized. If the number of error occurrences is found to be the minimum, the distance from the center of the target track to the minimum error position determines the MR offset.

However, the conventional MR offset measurement methods as described above have a problem such that the measurement takes a long time because it involves a micro jogging operation, it is difficult to select the optimal position for calculating the MR offset. For example, it is not clear which position should be selected as the optimal position when the magnitude of the detected burst signal shows a similar magnitude over a wide area. The case where the detected burst signal has a maximum value over a wide area occurs more frequently because the widths of the recording head and the recording head do not coincide.

It is an object of the present invention to provide a method for quickly and easily detecting the offset of a magnetoresistive head in a hard disk drive.

Another object of the present invention is to provide a computer-readable recording medium storing a program suitable for the above method.

MR offset detection method of a hard disk drive according to the present invention

Recording the second servo patterns based on the first servo patterns recorded on the disc so as not to overlap the first servo pattern in the track direction;

Reading the first servo pattern while following a target track to which the MR offset is to be measured based on the second servo pattern; And

And measuring the MR offset by the difference between the center position of the target track and the position represented by the first servo pattern.

The method according to the present invention obtains the position information represented by the reference servo pattern while following the target track based on the final servo pattern recorded through the servo copying process, and obtains the position information and the target track represented by the reference servo pattern. By comparing the position information, the MR offset can be measured quickly and simply.

The features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the invention shown in the accompanying drawings.

Reference will be made in detail to exemplary embodiments of the invention, wherein like reference numerals denote like elements. In addition, in order to simplify the description, anything that is not novel or well known to those skilled in the art will be omitted.

3 shows the disks assembled in the hard disk drive.

The hard disk drive includes a reference disk and one or more blank disks. For convenience of description, the number of blank disks is shown as two sheets in FIG. 3.

4A and 4B are diagrams for schematically showing a self servo recording method. Reference servo pattern 52 is referenced to record the final servo pattern 54. 4A shows an example in which the reference servo pattern 52 is recorded in a radio image on the disc. The number of radiations is appropriately selected.

Referring to FIG. 4B, the reference servo pattern 52 is recorded on one of the disks (reference disk) and only on one side of the reference disk, and with reference to the reference servo pattern 52 recorded on the reference disk, The final servo pattern 54 is recorded on the other side of the reference disk. The reference disc may be made before the disc is assembled or after the disc is assembled.

When the final servo pattern 54 is recorded, the reference servo pattern 52 is placed in the data area. As such, the process of recording the final servo pattern 54 with reference to the reference servo pattern 52 is referred to as a servo copy process.

When the final servo pattern 54 is written, the reference servo pattern 52 is no longer needed and therefore erased so as not to act as noise for the data area later.

However, in the present invention, the reference servo pattern 52 is not erased and the MR offset is measured using the same.

5 is a schematic view of the MR offset measurement method according to the present invention.

Referring to Figure 5, reference servo patterns 54 are recorded in the T1 and T2 tracks. The reference servo patterns 52 are recorded in an old servo sector, and the reference servo patterns 52 become old data sectors. In the servo copying process, the read head records the final servo patterns 54 at the position of T3 by the recording head while following the T1 track. At this time, the final servo pattern 54 is recorded between the reference servo patterns 52 so as not to overlap with the existing reference servo patterns 54 in the track direction. The final servo patterns 54 are recorded in a new servo sector, and between the final servo patterns 54 become new data sectors. That is, when the final servo pattern 54 is recorded, the reference servo pattern 52 is located in the data area.

Here, since the servo copying process is to follow the T1 track by the read head and write to the T3 position by the recording head, the difference between the T1 track and the T3 position becomes the position difference, that is, MR offset, between the read head and the recording head.

The servo pattern includes a gray code for indicating a track address and bursts for obtaining a Position Error Signal (PES). If the reference servo pattern 52-1 in the data area of the T3 track is read while following the T3 track by the final servo pattern 54, the position of the T3 track and the reference servo pattern 52-1 are read. The MR offset can be determined by the difference from the position indicated.

At this time, in order to read the reference servo pattern 52-1, it is required to operate in the servo read mode instead of the data read mode.

6 is a flowchart illustrating an MR offset measuring method according to the present invention.

First, the reference servo pattern is recorded on the disc. (S602) The reference disc on which the reference servo pattern is recorded may be prepared before the disc is assembled or may be prepared after the disc is assembled. Typically, writing a reference servo pattern on a disk is performed by a known servo writer.

The final servo pattern is recorded with reference to the reference servo pattern (s604). At this time, the reference servo pattern is left without being erased.

The reference servo pattern recorded in the data area of the target track is read while referring to the target track whose MR offset is to be measured by referring to the final servo pattern (s606).

The MR offset is calculated based on the difference between the position of the target track and the position indicated by the read reference servo pattern (s608).

The track address can be known by the gray code of the reference servo pattern, and the offtrack amount can be known by the burst.

The MR offset in the target track is calculated as follows.

MR offset in the target track = center position of the target track (center position of the track indicated by the gray code of the reference servo pattern + offtrack amount indicated by the burst of the reference servo pattern)

The obtained MR offset is stored in a maintenance cylinder of the disk or in an inactive memory (s610).

As illustrated and described with reference to FIG. 6, the MR offset detection method of the hard disk drive according to the present invention calculates an MR offset using a reference servo pattern read while following a track with reference to a final servo pattern.

Since the MR offset measuring method according to the present invention does not involve a micro jogging process, it can be seen that the MR offset can be measured quickly and simply.

In general, a disk is composed of a plurality of zones, and each zone has spare tracks for defect processing. In the method of the present invention, the reference servo pattern is left only in the spare tracks when the final servo pattern is recorded, and the MR offset is measured using this to minimize noise in the data area.

7 shows a configuration of a hard disk drive 10 to which the present invention is applied. The drive 10 includes at least one magnetic disk 12 that is rotated by a spindle motor 14. Hard disk drive 10 also includes a head 16 positioned adjacent to disk surface 18.

The head 16 can read or write information to the rotating disk 12 by sensing and magnetizing the magnetic field of each disk 12. Typically each head 16 is associated with a respective disk surface 18. On the other hand, although shown as a single head 16 in FIG. 1, it is substantially composed of a recording head for magnetizing the disk 12 and a separate reading head for sensing the magnetic field of the disk 12. It must be understood. Typically, the writing head consists of a magnetic circuit having a gap, and the reading head consists of a magneto-resistive (MR) element. Head 16 is also commonly referred to as a head.

Head 16 may be integrated into slider 20. The slider 20 is structured to create an air bearing between the head 16 and the disk surface 18. The slider 20 is coupled to the head gimbal assembly 22. The head gimbal assembly 22 is attached to an actuator arm 24 having a voice coil 26. The voice coil 26 is located adjacent to the magnetic assembly 28 that specifies the voice coil motor 30 (VCM). The current supplied to the voice coil 26 generates a torque that rotates the actuator arm 24 relative to the bearing assembly 32. Rotation of actuator arm 24 will move head 16 across disk surface 18.

The information is typically stored in concentric circular tracks on the disc 12. Each track 34 generally includes a plurality of sectors. Each sector includes a data field and an identification field (also called a servo field). The identification field consists of a gray code identifying a sector and a track (cylinder), and burst signals for detecting the degree to which the head 16 deviates from the track center. The head 16 is moved across the disk surface 18 by the movement of the actuator arm.

8 shows an electrical circuit of a hard disk drive to which the present invention is applied.

As shown in FIG. 8, the hard disk drive according to the present invention includes a disk 12, a head 16, a preamplifier 210, a write / read channel 220, a host interface 230, and a controller 240. , A memory 250, a temperature sensor 260, and a voice coil motor (VCM) driver 270.

The circuit configuration including the preamplifier 210 and the write / read channel 220 above will be referred to as a write / read circuit.

The memory 250 stores various programs and data for controlling the hard disk drive, and in particular, a program for executing the MR offset measuring method according to an embodiment of the present invention. In this case, the memory 250 is designed as a nonvolatile memory.

First, the operation of a general hard disk drive will be described.

In the data read mode, the hard disk drive amplifies the electrical signal sensed by the head 16 (also called a head) from the disk 12 in the preamplifier 210 to facilitate signal processing. Then, in the recording / reading channel 220, the amplified analog signal is encoded into a digital signal that can be read by a host device (not shown), converted into stream data, and transmitted to the host device through the host interface 230. send.

In contrast, in the data write mode, the hard disk drive receives data from a host device and temporarily stores the data in a buffer (not shown) embedded in the host interface 230, and sequentially outputs the data stored in the buffer. The write / read channel 220 converts the write current amplified by the preamplifier 210 to the disk 12 via the head 16 after conversion to a binary data stream suitable for the write channel.

The MR offset detection process by the controller 240 will be described in detail.

The controller 240 performs a servo copy routine to record the final servo pattern on the disk. At this time, the reference servo pattern is left without being erased.

The controller 240 reads the reference servo pattern recorded in the data area of the target track while referring to the target track with reference to the final servo pattern, and calculates the MR offset with reference to the position indicated by the read reference servo pattern. The controller 240 stores the obtained MR offset in a maintenance cylinder of the disk or in an inactive memory. In subsequent write and read operations, the controller 240 applies the stored MR offset.

The invention can be practiced as a method, apparatus, system, or the like. When implemented in software, the constituent means of the present invention are code segments that necessarily perform the necessary work. The program or code segments may be stored in a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network. Processor readable media includes any medium that can store or transmit information. Examples of processor readable media include electronic circuits, semiconductor memory devices, ROMs, flash memory, erasable ROM (EROM), floppy disks, optical disks, hard disks, optical fiber media, radio frequency (RF) networks, Etc. Computer data signals include any signal that can propagate over transmission media such as electronic network channels, optical fibers, air, electromagnetic fields, RF networks, and the like.

Specific embodiments shown and described in the accompanying drawings are only to be understood as an example of the present invention, not to limit the scope of the invention, but also within the scope of the technical spirit described in the present invention in the technical field to which the present invention belongs As various other changes may occur, it is obvious that the invention is not limited to the specific constructions and arrangements shown or described. That is, it is a matter of course that the present invention can be applied not only to various disk drives including hard disk drives, but also to various kinds of data storage devices.

As described above, the MR offset detection method of the hard disk drive according to the present invention reads the reference servo pattern while following the track with reference to the final servo pattern, and uses the position information indicated by the reference servo pattern to adjust the MR offset. The calculation has the effect of measuring the MR offset quickly and simply.

Claims (4)

A method of detecting an offset (MR offset) between a recording head and a reading head of a hard disk drive, Recording the second servo patterns based on the first servo patterns recorded on the disc so as not to overlap the first servo pattern in the track direction; Reading the first servo pattern while following a target track for measuring an MR offset based on the recorded second servo pattern; And And measuring an MR offset by a difference between a center position of the target track and a position represented by the first servo pattern. The method of claim 1, And the first servo pattern is a reference servo pattern recorded by the servo writer and the second servo pattern is a final servo pattern recorded with reference to the reference servo pattern. The method of claim 2, And the disc is composed of a plurality of zones, each zone has spare tracks for defect processing, and the target track is one of the spare tracks. A recording medium that can be read by a computer that has recorded a program for detecting an offset (MR offset) between a recording head and a reading head of a hard disk drive, Recording the second servo patterns based on the first servo patterns recorded on the disc so as not to overlap the first servo pattern in the track direction; Reading the first servo pattern while following a target track for measuring an MR offset based on the recorded second servo pattern; And And a program for performing a process of measuring an MR offset by a difference between a center position of the target track and a position represented by the first servo pattern.

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