JP2010061746A - Magnetic storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the worsening of an error rate by matching a write position and a read position even if a track pitch abnormality occurs in a magnetic storage device. <P>SOLUTION: A QM value or an AGC gain value is measured in a plurality of offset positions where a head is offset from a track center, and a polynomial expression representing a relationship between the QM value or the AGC gain value and each offset amount is generated from the QM value or the AGC gain value and the offset position. An offset amount which makes zero a shifting amount from the track center from the generated polynomial expression is obtained as a correction value of the track pitch unevenness of a servo pattern is obtained. The track pitch unevenness is corrected by controlling the position of a head based on the correction value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic storage device, and more particularly to a magnetic storage device that corrects a deviation of a head from a track center (hereinafter referred to as a track center).

  A magnetic storage device such as a magnetic disk device magnetically records information on a magnetic recording medium with a write head (hereinafter referred to as “write”), and reproduces information from the magnetic recording medium with a read head (hereinafter referred to as “read”). . The head is positioned on a target track for writing or reading data based on positioning information (hereinafter referred to as servo information) written in advance on the magnetic recording medium. The servo pattern of the servo information is written according to the determined track feed amount, and the head is positioned using the servo data reproduced from the servo pattern at the time of data writing and reading.

  FIG. 1 is a diagram for explaining the relationship between a write head and a read head. As shown in FIG. 1, the write head 1 and the read head regardless of the MR (Magneto-Resistive or Magneto-Resistance) head, the GMR (Giant MR) head, the TMR (Tunneling MR) head, the horizontal recording method, and the vertical recording method. The core widths of the two are generally different, and a gap G is physically generated between the write head 1 and the read head 2.

  FIG. 2 is a diagram for explaining the on-track positional deviation between the write head and the read head. The change of the on-track position of the heads 1 and 2 on the magnetic disk 5 is generally head position control by a rotary type VCM (Voice Coil Motor). In FIG. 2, an arm (not shown) that moves the heads 1 and 2 rotates around a fulcrum C. However, as shown in FIG. 2, since the heads 1 and 2 have a yaw angle Y with respect to the track on the magnetic disk 5, the write head 1 is turned on during writing at a track position with the Yaw angle Y. The on-track position ROP of the read head 2 when reading the same track position is different from the track position WOP. Since the Yaw angle Y differs depending on the radial position on the magnetic disk 5, the deviation amount of the on-track position corrects the core deviation amount of the write head 1 and the read head 2 according to the radial position.

  When writing the servo pattern to the magnetic disk 5, it is ideal that the servo pattern is written at a constant feed pitch. However, unstable rotation of the VCM, STW (Servo Track Writer) pin contact with the magnetic disk 5, peripheral The track pitch unevenness of the servo pattern occurs due to error factors such as environment (vibration and shock). When the error factor increases, track pitch unevenness (so-called pitch abnormality) that cannot be ignored occurs. Such a problem similarly occurs when a servo pattern is written to the magnetic disk 5 after the magnetic disk device is assembled and when a servo pattern is written by STW in the state of the magnetic disk 5.

  FIG. 3 is a diagram for explaining core deviation correction of a normal track. In FIG. 3 and FIGS. 4 and 5 described later, T1,... Indicate tracks, and D1,. In the case of the normal track shown in FIG. 3, data can be written to the target track by performing the above-described core deviation correction. For example, if the core deviation due to the Yaw angle Y is 4 tracks, the read head 2 needs to be on-tracked to the track T1 to write data to the track T1.

  In contrast, the case where the track pitch is narrow will be described with reference to FIGS.

  FIG. 4 is a diagram for explaining a write operation at a narrow track pitch. As shown in FIG. 4, when straddling a portion where the feed pitch is narrow, in the case of FIG. 3, even if writing can be performed at the position of the track T <b> 1 at the time of writing, in FIG. This causes a difference from the core deviation correction amount, and writing to the center of the track T1 is impossible. For example, in order to write data to the track T1, the read head 2 needs to be on-track to the track T4. However, since there is a portion where the track pitch is narrow (track T2), the data write position in the track T1 is shifted. End up.

FIG. 5 is a diagram for explaining the read operation at a narrow track pitch. In the case of FIG. 5, even if the read head 2 is positioned at the center position of the track T1 at the time of reading, the position where the data is written by the write head 1 is not at the center of the track T1, so that the data can be read normally. This is not possible and an error occurs in the read data. For example, when the data of the track T1 is read by the read head 2, the center position trc of the read head 2 coincides with the center of the original track T1, but the position where the data is written by the write head 1 is shifted from the center position trc. Therefore, the normal reproduction waveform that should be output is not output from the read head 2, and the error rate is deteriorated.
JP 2001-28111 A Japanese Patent Application Laid-Open No. 2007-164887 JP 2007-164890 A Japanese Patent No. 3024184

  Conventionally, in the case of a magnetic storage device employing a rotary head position control that controls the position of a head on a magnetic recording medium by rotating an arm, if the track pitch is abnormal, the write position of the write head and the read head There is a problem that it is difficult to align the lead position and the error rate deteriorates.

  When the error rate deteriorates, the number of retry operations increases and the processing speed and reliability of the magnetic storage device decrease.

  Accordingly, an object of the present invention is to provide a magnetic storage device that can prevent the deterioration of the error rate by matching the write position and the read position even when a track pitch abnormality occurs.

  According to one aspect of the present invention, a measurement circuit that measures a quality monitor value representing signal quality from a signal read from a magnetic recording medium by the head, and the head is offset from a track center of a target track on the magnetic recording medium. Generating a polynomial that represents the relationship between the quality monitor value at each offset position and each offset amount, and calculating the offset amount that makes the deviation amount from the track center zero from the polynomial, and based on the offset amount There is provided a magnetic storage device including a control unit for controlling the position of the head so as to correct the track pitch unevenness of the target track.

  According to one aspect of the present invention, an automatic gain control circuit that controls a gain value so as to keep the waveform level of the signal constant from a signal read from the magnetic recording medium by the head, and the head on the magnetic recording medium A calculation unit that generates a polynomial that represents a relationship between each offset amount and a gain value at a plurality of offset positions offset from the track center of the target track, and calculates an offset amount that makes a deviation amount from the track center zero from the polynomial; There is provided a magnetic storage device comprising a control unit for controlling the position of the head so as to correct the track pitch unevenness of the target track based on the offset amount.

  According to the disclosed magnetic storage device, even if a track pitch abnormality occurs, it is possible to prevent the error rate from deteriorating by combining the write position and the read position.

  In the disclosed magnetic storage device, a quality monitor (QM) value or an automatic gain control (AGC) gain value is measured at a plurality of offset positions where the head (head core center) is offset from the track center. Then, a polynomial representing the relationship between the QM value or AGC gain value and each offset amount is generated from the QM value or AGC gain value and the offset position. From the generated polynomial, an offset amount that makes the deviation amount from the track center zero is obtained as a correction value of the track pitch unevenness of the servo pattern. The track pitch unevenness is corrected by controlling the position of the head based on this correction value (offset amount).

  The offset amount may be written on the magnetic recording medium and the offset amount of the servo pattern may be corrected by reading the offset amount.

  Thereby, even if a track pitch abnormality occurs, it is possible to prevent the error rate from deteriorating by combining the write position and the read position.

  Since the error rate can be prevented from deteriorating, the number of retry operations is reduced and the processing speed and reliability of the magnetic storage device are improved.

  FIG. 6 is a block diagram showing a magnetic storage device in one embodiment of the present invention. In this embodiment, the present invention is applied to a magnetic disk device.

  As shown in FIG. 6, the magnetic disk device 10 includes a disk enclosure (DE) 11 and a printed circuit board (PCB) 12. The PCB 12 is connected to a host device 13 such as a personal computer.

  The DE 11 includes a magnetic disk 5, a DC motor (DCM) 111 that rotates the magnetic disk 5, a VCM (Voice Coil Motor) 112 that moves an arm 113 provided at the tip of the head 114, and a head amplifier 115. The DE 11 is shielded from the outside through a filter (not shown) in order to protect the magnetic disk 5 and the head 114 from dust. The head 114 includes the write head 1 and the read head 2 as described with reference to FIG. The head 114 performs a read operation and a write operation while floating from the surface of the rotating magnetic disk 5. The basic configuration itself of DE 11 is well known, and a basic configuration other than that shown in FIG. 6 may be used as DE 11.

  The PCB 12 includes an MCU (Micro Controller Unit) 121, a servo controller (SVC: SerVo Controller) 122, a read channel (RDC: ReaD Channel) 123, a hard disk controller (HDC: Hard Disk Controller) 124, which are connected as shown in FIG. And a data buffer 125. The RDC 123 includes a quality monitor (QM) measurement circuit 23, an automatic gain control (AGC) circuit 230, and the like. The PCB 12 transmits / receives data to / from the host device 13 and controls the DE 11. The basic configuration of the PCB 12 is well known, and a basic configuration other than that shown in FIG. 6 may be used as the PCB 12. The MCU 121, the HDC 124, and further the RDC 123 may be integrated in a single large scale integrated circuit (LSI). Needless to say, the MCU 121 can be configured by various processors.

  The MCU 121 controls the DCM 111 that rotates the magnetic disk 5 via the SVC 122, and functions as a control unit that rotates the magnetic disk 5 in a steady manner.

  The tracks on the magnetic disk 5 are classified into a servo part in which servo information indicating the position of the head 114 is stored and a data part in which data is stored. Servo information read from the track by the head 114 is decoded into position information by the RDC 123 and supplied to the MCU 121. The MCU 121 also functions as a control unit that controls the VCM 112 via the SVC 122 so as to accurately position the head 114 on the track based on this position information and address information supplied from the HDC 124 described later.

  The HDC 124 transmits and receives data to and from the host device 13. At the time of writing, in response to a write command from the host device 13, write data input from the host device 13 is temporarily stored in the data buffer 125 via the HDC 124, and a write signal from the RDC 123 via the head amplifier 115. It is supplied to the head 114. In addition, address information included in the write command is supplied to the MCU 121 via the HDC 124. As a result, the write signal is written to the magnetic disk 5 by the head 114.

  On the other hand, at the time of reading, in response to a read command from the host device 13, a read signal read from the magnetic disk 5 by the head 114 is supplied to the RDC 123 via the head amplifier 115, and read data is supplied from the RDC 123 to the HDC 124. The The AGC circuit 230 in the RDC 123 operates so as to keep the waveform level of the read signal constant. The AGC circuit 230 itself is a well-known circuit. In addition, address information included in the read command is supplied to the MCU 121 via the HDC 124. The read data is temporarily stored in the data buffer 125 via the HDC 124 and is output from the HDC 124 to the host device 13. The operation of the RDC 123 during writing and reading is controlled by the MCU 121.

  The RDC 123 generally includes a quality monitor (QM) function, and the signal quality of the read signal is monitored by the QM measurement circuit 23. The error rate takes time to measure. On the other hand, the QM value representing the signal quality of the read signal has a high correlation with the error rate. For this reason, in general, in order to shorten the time, the signal quality is often monitored using the QM value measured by the QM measurement circuit 23 instead of the error rate. The QM measurement circuit 23 itself is a known circuit. The QM value measured by the QM measurement circuit 23 is supplied from the RDC 123 to the MCU 121.

  As described with reference to FIG. 1, since there is a gap G between the write head 1 and the read head 1, it is necessary to correct the core deviation amount by the Yaw angle Y. Therefore, track pitch unevenness (track pitch abnormality) is detected in a test process before shipment of the magnetic disk device 10. In this embodiment, this track pitch unevenness is detected using the QM value.

  FIG. 7 is a diagram illustrating an example of QM values measured by offsetting tracks. The QM value shown in FIG. 7 is measured by offsetting the head 114 (head core center) from the track center of the target track. In FIG. 7 and FIGS. 8 to 10, 15 and 16, which will be described later, the vertical axis indicates the QM value (arbitrary unit), the horizontal axis indicates the offset amount (%), and the offset amount is an offset amount for one track of 200. It is shown as%. As can be seen from FIG. 7, the QM value indicates a U-shaped (or bathtub-type) change with respect to the offset amount.

  In this embodiment, QM values are measured at a plurality of offset positions, preferably at three or more offset positions with respect to the target track, in a test process before shipment. FIG. 8 is a diagram showing an example in which QM values are measured at three offset positions in FIG. In FIG. 8, □ marks indicate QM values at three offset positions.

  A polynomial that represents the relationship between the QM value and the offset amount is generated from the measured QM value and the three offset positions. In the case of FIG. 8, the following polynomial (1) can be generated. In this example, the polynomial is a quadratic expression.

y = 0.0003208x ² −0.0002809x + 3.0545677 Formula (1)
The polynomial (1) is represented by the following polynomial (2) when expressed by a general formula. Here, A, B, and C are coefficients.

Y = A × X ² + B × X + C Formula (2)
By differentiating the polynomial (2) generated in this way, the shift amount of the track center of the target track can be found. Specifically, in the polynomial (2), an offset amount X for correcting the deviation amount so that Y becomes zero can be calculated from the following equation (3). Since the offset amount X is for correcting the shift amount, the absolute value is the same as the shift amount.

X = −B / 2A Formula (3)
In the case of FIG. 8, the offset amount X is X = − (− 0.0002809) / (2 × 0.0003208) = 0.4.

  In FIG. 8, when there is almost no center deviation of the target track, the QM values are measured at the three offset positions. Therefore, the offset amount in this case can be calculated as 0.4%, and there is almost no track center deviation. It could be confirmed.

  The generation of the polynomial (2) and the calculation of the expression (3) are performed by the MCU 121. Therefore, the MCU 121 also functions as a calculation unit that executes generation and calculation of polynomials.

  FIG. 9 is a diagram illustrating an example of the QM value measured when the track center is relatively displaced. FIG. 10 is a diagram showing an example in which QM values are measured at three offset positions in FIG. In the case of FIG. 10, the following polynomial (4) can be generated.

y = 0.0003685x ² −0.0152067x + 3.11889042 Formula (4)
In the case of FIG. 9, the center deviation of the target track is actually about 21%. On the other hand, when the QM values are measured at the three offset positions in FIG. 10 and the offset amount X is calculated, the offset amount X is X = − (− 0.0152067) / (2 × 0.0003685) = − 20.6. It was confirmed that the center deviation of the track can be measured accurately.

  By the way, the track density on the magnetic disk is increasing due to the increase in the surface density of the magnetic disk used in recent magnetic disk devices. In order to increase the track density, the accuracy of positioning the head on the target track is very important. At present, the mainstream technique is to improve the positioning accuracy by learning the rotation synchronization component and embedding it in the servo section of the track, and reading it when the head is on track and using it for correction.

  FIG. 11 is a diagram illustrating an example of a track format. As shown in FIG. 11, a servo part and a data part are provided on the track. Servo information si1, si2 and position correction information pci1, pci2 are written in the servo section. For example, data sectors ds1, ds2, and ds3 are written in the data portion.

  FIG. 12 is a diagram for explaining an example of a method for learning position correction information, and FIG. 13 is a diagram for explaining an example of use of position correction information.

  First, an RRO (Repeatable Run-Out) component synchronized with the rotation of the magnetic disk 5 generated by demodulating the servo signals in the servo information si1 and si2 shown in FIG. 12 is learned, and the difference from the ideal center of the target track. Calculate information. Then, the difference information calculated for each servo frame is written to the position correction information pci1 and pci2.

  When the target track is on-track, the position correction information pci1 and pci2 are read, and the RRO component for each servo frame is shifted and positioned as shown in FIG. 13, thereby removing the RRO component and improving the positioning accuracy. be able to. If it takes time to learn the RRO component, it is ideally possible to completely remove the RRO component. However, this takes too much test time, so the learning time is optimized according to the required positioning accuracy.

  FIG. 14 is a diagram for explaining a correction example in which the center deviation amount is included as a DC component in the position correction information.

  The offset amount X obtained from the QM value, that is, the DC offset value, is written in the positioning correction information pci1 and pci2 as a DC component, and is written, and this positioning correction information pci1 and pci2 is read from each servo unit at the time of reading. By causing the head 114 to be on-track while reading, the DC component is corrected, and the track pitch unevenness during servo writing can be corrected. As a result, it is possible to prevent the error rate from deteriorating due to track pitch unevenness during servo writing.

  FIG. 15 is a diagram illustrating an example of the QM value measured when the track center is largely deviated due to track pitch unevenness during servo writing. FIG. 16 is a diagram showing an example in which QM values are measured at three offset positions in FIG.

  When the track center deviation due to the track pitch unevenness during servo writing is large, the offset amount is about 42% in the example of FIG. On the other hand, the offset amount X calculated using the polynomial (2) and (3) is about 71%, and the offset amount X cannot be calculated accurately. Therefore, if the target track has a large track center deviation of, for example, about 42%, the influence on adjacent tracks also increases. Therefore, it is determined that the track pitch deviation is too large and this target track is registered as a defective track. It ’s fine. For a defective track, a redundant track by a known technique may be registered.

  FIG. 17 is a flowchart for explaining test processing including registration of such a defective track. In FIG. 17, in step S1, the track number of the target track on the magnetic disk 5 is set as the start track number. In step S2, data is written to the target track by the head 114. In step S3, the QM value of the target track is measured by the QM measurement circuit 23. In step S4, the amount of deviation of the target track from the track center, that is, the offset amount X is calculated by the MCU 121 using the QM value. In step S5, it is determined whether or not the deviation amount, that is, the offset amount X is within the correction range.

  When the deviation of the target track from the track center is as large as about 42% as described above, the determination result in step S5 is NO. In this case, in step S6, the MCU 121 determines that the target track is a defective track, registers the defective track in the memory in the magnetic disk device 10, and the process proceeds to step S7. The memory in the magnetic disk device 10 may be an internal memory of the MCU 121 or a memory not shown. In step S7, the track number is incremented by “1”, and the process returns to step S2.

  On the other hand, if the decision result in the step S5 is YES, the calculated offset amount X is put in the positioning correction information pci1 and pci2 as a DC component in the step S8, and the positioning correction information in which the offset amount X is put in the step S9. Write pci1 and pci2 to the target track. In step S10, it is determined whether or not the target track is the last track on the magnetic disk 5. If the determination result is NO, the process returns to step S7. If the decision result in the step S10 is YES, the process advances to another well-known process (post-process) of the test process.

  By the way, the read signal output from the head 114 is supplied to the RDC 123 via the head amplifier 115, and the AGC circuit 230 that operates to keep the waveform level of the read signal constant operates in the RDC 123 to control the gain value. The gain value (hereinafter referred to as the AGC gain value) controlled by the AGC circuit 230 becomes smaller as the read signal waveform level is larger because the head 114 is closer to the track center of the target track, and the read signal waveform level is smaller. Since 114 is deviated from the track center of the target track, it becomes large.

  Therefore, the relationship between the AGC gain value of the AGC circuit 230 and the offset amount is the same as the relationship between the QM value and the offset amount. Therefore, the offset amount X can be calculated using the AGC gain value instead of the QM value.

  FIG. 18 is a diagram illustrating an example of the AGC gain value measured by offsetting a track. In FIG. 18, the vertical axis indicates the AGC gain value (arbitrary unit), the horizontal axis indicates the offset amount (%), and the offset amount is illustrated with the offset amount for one track being 200%. As can be seen from FIG. 18, the AGC gain value shows a U-shaped (or bathtub-type) change with respect to the offset amount.

  Therefore, as in the case of obtaining the track center deviation amount (offset amount X) using the QM value, the offset amount X can be obtained in the same manner from the AGC gain value of the AGC circuit 230, and the offset amount X is positioned. The correction information pci1 and pci2 are inserted and written as DC components, and when reading, the head component 114 is on-tracked while reading the positioning correction information pci1 and pci2 from each servo unit, so that the DC component is corrected and servo is performed. Track pitch unevenness during writing can be corrected.

  As described above, according to this embodiment, it is possible to prevent the error rate from deteriorating by combining the write position and the read position even if a track pitch abnormality occurs. In addition, since the error rate can be prevented from deteriorating, the number of retry operations is reduced and the processing speed and reliability of the magnetic storage device are improved.

  The magnetic recording medium is not limited to a magnetic disk, but may be other than a disk shape. In short, if the magnetic head is a magnetic recording medium used in a magnetic storage device in which the write head and the read head have a yaw angle with respect to the track according to the position on the magnetic recording medium, the track pitch unevenness of the servo pattern Therefore, the present invention can be applied.

The following additional notes are further disclosed with respect to the embodiment including the above examples.
(Appendix 1)
A measurement circuit for measuring a quality monitor value representing the signal quality from the signal read from the magnetic recording medium by the head;
The head generates a polynomial that represents the relationship between the quality monitor values at a plurality of offset positions offset from the track center of the target track on the magnetic recording medium and each offset amount, and the deviation amount from the track center is calculated from the polynomial. A calculation unit for obtaining an offset amount to be zero;
A magnetic storage device comprising: a control unit that controls the position of the head so as to correct track pitch unevenness of the target track based on the offset amount.
(Appendix 2)
Write means for writing the offset amount to the target track by the head;
Read means for reading from the target track by the head,
The magnetic storage device according to claim 1, wherein the control unit controls the position of the head so as to correct a track pitch unevenness of the target track based on the read offset amount.
(Appendix 3)
The magnetic storage device according to appendix 2, wherein the writing means writes the offset amount to a servo section of the target track.
(Appendix 4)
The servo unit stores position correction information including difference information from the ideal center of the target track calculated by learning a RRO (Repeatable Run-Out) component synchronized with the rotation of the magnetic recording medium,
The magnetic storage device according to appendix 3, wherein the write means writes the offset amount into the servo unit so as to be included in the position correction information.
(Appendix 5)
The magnetic storage according to any one of appendices 1 to 4, wherein the control unit controls the position of the head so as to correct track pitch unevenness of the servo pattern of the target track based on the read offset amount. apparatus.
(Appendix 6)
The magnetic storage device according to any one of appendices 1 to 5, wherein the control unit registers the target track as a defective track when the offset amount is out of a correction range.
(Appendix 7)
The magnetic storage device according to any one of appendices 1 to 6, wherein the calculation unit and the control unit are configured by a single processor.
(Appendix 8)
Any one of appendices 1 to 7, wherein the head includes a write head and a read head having a yaw angle with respect to each track according to a position on the magnetic recording medium, and a gap formed therebetween. 2. A magnetic storage device according to claim 1.
(Appendix 9)
An automatic gain control circuit for controlling the gain value so that the waveform level of the signal is kept constant from the signal read from the magnetic recording medium by the head;
The head generates a polynomial representing the relationship between the gain value at each offset position offset from the track center of the target track on the magnetic recording medium and each offset amount, and the deviation from the track center is zero from the polynomial. A calculation unit for obtaining an offset amount to be
A magnetic storage device comprising: a control unit that controls the position of the head so as to correct track pitch unevenness of the target track based on the offset amount.
(Appendix 10)
Write means for writing the offset amount to the target track by the head;
Read means for reading from the target track by the head,
The magnetic storage device according to appendix 9, wherein the control unit controls the position of the head so as to correct track pitch unevenness of the target track based on the read offset amount.
(Appendix 11)
The magnetic storage device according to appendix 10, wherein the write means writes the offset amount to a servo portion of the target track.
(Appendix 12)
The servo unit stores position correction information including difference information from the ideal center of the target track calculated by learning a RRO (Repeatable Run-Out) component synchronized with the rotation of the magnetic recording medium,
The magnetic storage device according to appendix 11, wherein the writing means writes the offset amount to the servo unit so as to be included in the position correction information.
(Appendix 13)
The magnetic storage according to any one of appendices 9 to 12, wherein the control unit controls the position of the head so as to correct track pitch unevenness of the servo pattern of the target track based on the read offset amount. apparatus.
(Appendix 14)
The magnetic storage device according to any one of appendices 9 to 13, wherein the control unit registers the target track as a defective track when the offset amount is out of a correction range.
(Appendix 15)
The magnetic storage device according to any one of appendices 9 to 14, wherein the calculation unit and the control unit are configured by a single processor.
(Appendix 16)
Any one of appendices 9 to 15, wherein the head includes a write head and a read head having a yaw angle with respect to each track according to a position on the magnetic recording medium, and a gap formed therebetween. 2. A magnetic storage device according to claim 1.

  While the present invention has been described with reference to the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and various modifications and improvements can be made within the scope of the present invention.

It is a figure explaining the relationship between a write head and a read head. It is a figure explaining the on-track position shift of a write head and a read head. It is a figure explaining the core shift correction of a normal track. It is a figure explaining the write operation of the location of a narrow track pitch. It is a figure explaining the read operation of the location of a narrow track pitch. 1 is a block diagram illustrating a magnetic storage device according to an embodiment of the present invention. It is a figure which shows an example of the QM value measured by offsetting a track. It is a figure which shows an example which measured QM value in three offset positions in FIG. It is a figure which shows an example of the QM value measured when the track center shifted | deviated. It is a figure which shows an example which measured QM value in three offset positions in FIG. It is a figure which shows an example of a track format. It is a figure explaining an example of the learning method of position correction information. It is a figure explaining the usage example of position correction information. It is a figure explaining the example of a correction | amendment which put the center shift | offset | difference amount as DC component in position correction information. It is a figure which shows an example of the QM value measured when the track center shifted | deviated largely. It is a figure which shows an example which measured the QM value in three offset positions in FIG. It is a flowchart explaining a test process. It is a figure which shows an example of the AGC gain value measured by offsetting a track.

Explanation of symbols

5 Magnetic disk 10 Magnetic disk device 11 DE
12 PCB
13 Host device 23 QM measurement circuit 114 Head 121 MCU
122 SVC
123 RDC
124 HDC
125 data buffer

Claims (9)

A measurement circuit for measuring a quality monitor value representing the signal quality from the signal read from the magnetic recording medium by the head;
The head generates a polynomial representing the relationship between the quality monitor values at a plurality of offset positions offset from the track center of the target track on the magnetic recording medium and each offset amount, and the deviation amount from the track center is calculated from the polynomial. A calculation unit for obtaining an offset amount to be zero;
A magnetic storage device comprising: a control unit that controls the position of the head so as to correct track pitch unevenness of the target track based on the offset amount. Write means for writing the offset amount to the target track by the head;
Read means for reading from the target track by the head,
The magnetic storage device according to claim 1, wherein the control unit controls the position of the head so as to correct a track pitch unevenness of the target track based on the read offset amount.   The magnetic storage device according to claim 2, wherein the write unit writes the offset amount to a servo unit of the target track. The servo unit stores position correction information including difference information from the ideal center of the target track calculated by learning an RRO (Repeatable Run-Out) component synchronized with the rotation of the magnetic recording medium,
The magnetic storage device according to claim 3, wherein the write unit writes the offset amount to the servo unit so as to be included in the position correction information.   5. The magnetism according to claim 1, wherein the control unit controls the position of the head so as to correct a track pitch unevenness of a servo pattern of the target track based on the read offset amount. 6. Storage device.   The magnetic storage device according to claim 1, wherein the control unit registers the target track as a defective track when the offset amount is out of a correction range.   The magnetic storage device according to claim 1, wherein the calculation unit and the control unit are configured by a single processor.   8. The head according to claim 1, wherein the head includes a write head and a read head having a yaw angle with respect to each track according to a position on the magnetic recording medium, and a gap formed therebetween. The magnetic storage device according to claim 1. An automatic gain control circuit for controlling the gain value so that the waveform level of the signal is kept constant from the signal read from the magnetic recording medium by the head;
The head generates a polynomial that represents the relationship between the gain values and offset amounts at a plurality of offset positions offset from the track center of the target track on the magnetic recording medium, and the deviation from the track center is zero from the polynomial. A calculation unit for obtaining an offset amount to be
A magnetic storage device comprising: a control unit that controls the position of the head so as to correct track pitch unevenness of the target track based on the offset amount.

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