Magnetic disk device and control method for magnetic disk device

Abstract

The invention provides a magnetic disk device and a control method of the magnetic disk device, which can prevent quality deterioration of adjacent tracks without reducing writing performance. A magnetic disk device includes a magnetic disk, a magnetic head, and a controller that has an off-track write table, positions the magnetic head, and registers an address to which data is written in a track and a positioning error of the magnetic head with respect to the track at the address in the off-track write table. When writing data to a first sector, the controller corrects a positioning target position of the first sector on the basis of a positioning error of a second sector located at two tracks preceding the first sector in the radial direction.

Description

[0001] This application claims the priority of Japanese Patent Application No. 2023-134006 (filing date: August 21, 2023) as a basic application. The present application incorporates the entire contents of the basic application by reference. Technical Field

[0002] Embodiments of the present invention relate to a magnetic disk device and a control method of the magnetic disk device. Background Art

[0003] The magnetic disk device includes a magnetic disk, a magnetic head for writing / reading data from / to the magnetic disk, a system controller, and the like.

[0004] The system controller performs positioning control (hereinafter, also referred to as "positioning") of the magnetic head relative to a plurality of tracks formed in a substantially concentric circle on the magnetic disk. Due to positioning control errors, the magnetic head is positioned away from the track in the radial direction of the magnetic disk relative to the track. If the amount of deviation from the track is large, the risk of erasing data recorded in adjacent tracks increases. If writing is stopped with a small amount of deviation from the track in order to avoid data erasure, the writing performance decreases. Summary of the invention

[0005] Embodiments of the present invention provide a magnetic disk device and a control method of the magnetic disk device that can prevent the quality of adjacent tracks from being deteriorated without reducing the writing performance.

[0006] A magnetic disk device according to one embodiment comprises: a magnetic disk; a magnetic head positioned at a track of the magnetic disk arranged at a predetermined track pitch, for writing data to the track and reading data from the track; and a controller having an off-track write table for positioning the magnetic head, registering an address in the track where data is written and a positioning error of the magnetic head at the address relative to the track in the off-track write table, and when writing data to the first sector, the controller corrects the positioning target position of the first sector based on the positioning error of the second sector located two tracks ahead of the first sector in the radial direction.

[0007] In addition, in a control method of a magnetic disk device involved in one embodiment, the magnetic disk device includes a magnetic disk, a magnetic head and an off-track write table, the magnetic head is positioned at a track of the magnetic disk set at a predetermined track pitch, data is written to the track, and data is read from the track, the control method of the magnetic disk device includes: positioning the magnetic head; registering an address in the track where data is written and a positioning error of the magnetic head at the address relative to the track in the off-track write table; and when writing data to the first sector, correcting the positioning target position of the first sector based on the positioning error of the second sector located two tracks before the first sector in the radial direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a block diagram showing the structure of the magnetic disk device according to the first embodiment.

[0009] Figure 2 This is a diagram showing an example of a write process of the magnetic disk device according to the first embodiment.

[0010] Figure 3 This is a diagram showing an example of a write process of the magnetic disk device according to the first embodiment.

[0011] Figure 4 This is a block diagram showing an example of a control structure of the magnetic disk device according to the first embodiment.

[0012] Figure 5 This is a diagram showing an example of a control structure of the magnetic disk device according to the first embodiment.

[0013] Figure 6 It is a schematic diagram showing the correction amount of the target position and the positioning error of the data written to the sector of the first two tracks.

[0014] Figure 7 It is a schematic diagram showing the correction amount of the target position and the positioning error of the data written to the sector of the first two tracks.

[0015] Figure 8 It is a schematic diagram showing the correction amount of the target position and the positioning error of the data written to the sector of the first two tracks.

[0016] Fig. 9 It is a schematic diagram showing the correction amount of the target position and the positioning error of the data written to the sector of the first two tracks.

[0017] Fig.10 This is a schematic diagram for explaining an example of sampling processing.

[0018] Fig.11 This is a diagram showing an example of a write process of the magnetic disk device according to the second embodiment.

[0019] Fig.12 This is a diagram showing an example of a write process of the magnetic disk device according to the second embodiment.

[0020] Fig.13 This is a block diagram showing an example of a control structure of a magnetic disk device according to the second embodiment.

[0021] Fig.14 It is a schematic diagram showing the correction amount of the target position, the positioning error of the data written to the sector two tracks before, and the off-track slice with respect to the target sector.

[0022] Fig.15 It is a schematic diagram showing the correction amount of the target position and the off-track limit relative to the target sector.

[0023] Description of Reference Numerals

[0024] 1…disk device, 10…disk, 15…head, 15W…write head, 130…system controller, 611…off-track write table, 612…target position track generation circuit, 613…compression processing circuit, PE…positioning error, Trkm2, Trkm1, Trk0, Trk1, Trk2…track, TW1, TWm1…track width, WOS0m, WOS0p…off-track limit. DETAILED DESCRIPTION

[0025] Hereinafter, the embodiments will be described with reference to the drawings. Note that the drawings are merely examples and do not limit the scope of the invention.

[0026] Figure 1 This is a block diagram showing the structure of the magnetic disk device 1 according to the first embodiment.

[0027] like Figure 1 As shown, the magnetic disk device 1 includes a head disk assembly (HDA) described later, a driver IC 20, a head amplifier integrated circuit (hereinafter, sometimes referred to as a head amplifier IC or a preamplifier) ​​30, a volatile memory 70, a nonvolatile memory 80, a buffer memory 90, and a system controller 130 which is an integrated circuit of one chip. In addition, the magnetic disk device 1 is connected to a host system (host) 100.

[0028] The HDA has a magnetic disk (hereinafter referred to as a "disk") 10, a spindle motor (SPM) 12, an arm 13 carrying a magnetic head 15, and a voice coil motor (VCM) 14. The disk 10 is mounted on the spindle motor 12 and rotated by the drive of the spindle motor 12. The arm 13 and the voice coil motor 14 constitute an actuator. The actuator controls the movement of the magnetic head 15 mounted on the arm 13 to a predetermined position of the disk 10 by the drive of the voice coil motor 14. There may be two or more disks 10 and magnetic heads 15.

[0029] Hereinafter, data written to each part of the magnetic disk device 1 and an external device, such as the disk 10, may be referred to as written data, and data read from each part of the magnetic disk device 1 and an external device, such as the disk 10, may be referred to as read data. There may be a case where the written data is simply referred to as data, there may be a case where the read data is simply referred to as data, and there may be a case where the written data and the read data are collectively referred to as data.

[0030] The disk 10 is allocated with a user data area 10a that can be used by the user, a media cache area 10b that temporarily stores data (or commands) transmitted from the host 100 or the like before writing them to a predetermined area of ​​the user data area 10a, and a system area 10c that records information necessary for system management as areas where data can be written. Hereinafter, the direction perpendicular to the radial direction of the disk 10 is referred to as the circumferential direction. In addition, the media cache area 10b does not necessarily have to be allocated, and the system area 10c may be allocated to the nonvolatile memory 80 or the like.

[0031] The magnetic head (hereinafter also referred to as head) 15 mainly includes a slider, and includes a write head 15W and a read head 15R attached to the slider. The write head 15W writes data to the track of the disk 10. The read head 15R reads data recorded on the track of the disk 10.

[0032] In addition, the write head 15W may be referred to as simply the head 15, the read head 15R may be referred to as simply the head 15, and the write head 15W and the read head 15R may be collectively referred to as the head 15. The "track" is used to mean one of the multiple areas divided in the radial direction of the disk 10, one of the multiple areas divided in the circumferential direction of the disk 10, data written to a predetermined position of the disk 10, data written to a sector, and other various meanings. In addition, the width of the track in the radial direction is referred to as the track width, and the center position of the track width is referred to as the track center.

[0033] The driver IC 20 controls the driving of the spindle motor 12 and the VCM 14 under the control of the system controller 130 (specifically, the MPU 60 described later).

[0034] The head amplifier IC (preamplifier) ​​30 includes a read amplifier and a write driver. The read amplifier amplifies the read signal read from the disk 10 by the read head 15R and outputs it to the system controller 130 (specifically, the read / write (R / W) channel 40 described later). The write driver outputs a write current corresponding to the signal output from the R / W channel 40 to the write head 15W.

[0035] The volatile memory 70 is a semiconductor memory in which the stored data is lost when the power supply is cut off. The volatile memory 70 stores data required for processing in each part of the magnetic disk device 1, etc. The volatile memory 70 is, for example, a DRAM (Dynamic Random Access Memory) or an SDRAM (Synchronous Dynamic Random Access Memory).

[0036] The nonvolatile memory 80 is a semiconductor memory that records stored data even when power supply is cut off. The nonvolatile memory 80 is, for example, a NOR type or NAND type flash ROM (Flash Read Only Memory: FROM).

[0037] The buffer memory 90 is a semiconductor memory that temporarily records data or the like transmitted and received between the magnetic disk device 1 and the host 100. The buffer memory 90 may be formed integrally with the volatile memory 70. The buffer memory 90 is, for example, a DRAM, a SRAM (Static Random Access Memory), a SDRAM, a FeRAM (Ferroelectric Random Access Memory), or an MRAM (Magnetoresistive Random Access Memory).

[0038] The system controller (controller) 130 is implemented, for example, using a large-scale integrated circuit (LSI) called a system-on-a-Chip (SoC) in which a plurality of components are integrated into a single chip. The system controller 130 includes a read / write (R / W) channel 40, a hard disk controller (HDC) 50, and a microprocessor (MPU) 60. The system controller 130 is electrically connected to the driver IC 20, the head amplifier IC 30, the volatile memory 70, the nonvolatile memory 80, the buffer memory 90, and the host system 100.

[0039] The R / W channel 40 performs signal processing of read data transmitted from the disk 10 to the host 100 and write data transmitted from the host system 100 according to instructions from the MPU 60 described later. The R / W channel 40 has a circuit or function for measuring the signal quality of the read data. The R / W channel 40 is electrically connected to, for example, the head amplifier IC, the HDC 50, and the MPU 60.

[0040] The HDC 50 controls data transfer between the host system 100 and the R / W channel 40 according to instructions from the MPU 60 described later. The HDC 50 is electrically connected to the R / W channel 40, the MPU 60, the volatile memory 70, the nonvolatile memory 80, and the buffer memory 90, for example.

[0041] The MPU 60 is a main controller that controls each part of the magnetic disk device 1. The MPU 60 controls the VCM 14 via the driver IC 20 and performs servo control for positioning the head 15. In addition, the MPU 60 controls the spindle motor (SPM) 12 via the driver IC 20 to rotate the disk 10. The MPU 60 controls the writing of data to the disk 10 and selects the storage destination of the written data. In addition, the MPU 60 controls the reading of data from the disk 10 and controls the processing of the read data. The MPU 60 is connected to each part of the magnetic disk device 1. For example, the MPU 60 is electrically connected to the driver IC 20, the R / W channel 40, and the HDC 50.

[0042] The MPU 60 includes a write control unit 610 that controls a write process, and a read control unit 620 that controls a read process. The MPU 60 executes the processes of the above-mentioned units, such as the write control unit 610 and the read control unit 620, on firmware. In addition, the MPU 60 may include the above-mentioned units, such as the write control unit 610 and the read control unit 620, as circuits.

[0043] The write control unit 610 controls the data writing process according to the command from the host 100 or the like. The write control unit 610 controls the VCM 14 via the driver IC 20 to place the head 15 at a predetermined position on the disk 10 and write the data. Hereinafter, “positioning the center of the head 15 (write head 15W or read head 15R) at a predetermined position” or “positioning the center of the head 15 (write head 15W or read head 15R) at a predetermined position” may be referred to simply as “positioning the head 15 (write head 15W or read head 15R) at a predetermined position” or “positioning the head 15 (write head 15W or read head 15R) at a predetermined position”. In addition, “positioning the head 15 (write head 15W or read head 15R) at a predetermined position” or “positioning the head 15 (write head 15W or read head 15R) at a predetermined position” may be referred to simply as “positioning” or “positioning”.

[0044] The write control unit 610 configures the head 15 (write head 15W) to write data at a position that is a target during write processing (hereinafter, sometimes referred to as a positioning target position, a target position, or a target write position). The write control unit 610 configures the head 15 at the target write position to perform random writing. In other words, the write control unit 610 configures the head 15 at a predetermined circumferential position as a radial position that is a target during write processing (hereinafter, sometimes referred to as a target radial position, or a target write radial position) to randomly write data. For example, the write control unit 610 controls the head 15 to be configured at the target write radial position at a predetermined circumferential position to perform random writing on a predetermined sector.

[0045] The write control unit 610 can control the head 15 to be positioned at the target write position and to randomly write data at a predetermined position (hereinafter sometimes referred to as an actual position or actual write position). The actual write position may be the target write position or a position deviated from the target write position.

[0046] Hereinafter, “the center portion of the write head 15W deviates from a predetermined target writing position in the radial direction” may be described as “the write head 15W deviates from a predetermined track”.

[0047] In addition, the write control unit 610 has Figure 4 The write processing circuit C1 will be described later in the description of . In addition, the write processing circuit C1 may be provided outside the write control unit 610 .

[0048] The read control unit 620 controls the data read process according to the command from the host 100, etc. The read control unit 620 controls the VCM 14 via the driver IC 20 to place the head 15 at a predetermined position on the disk 10 and read the data. The read control unit 620 can read data randomly or sequentially.

[0049] The read control unit 620 configures the head 15 (read head 15R) at the target read position to read data. The read control unit 620 configures the head 15 at the target read position to read. In other words, the read control unit 620 controls the head 15 to be configured at the target read radius position at a predetermined circumferential position to read data. For example, the read control unit 620 controls the head 15 to be configured at the target read radius position at a predetermined circumferential position to read a predetermined sector. In addition, the read control unit 620 can control the head 15 along the target read path to read a predetermined track.

[0050] Here, the basic concept of the embodiment is described.

[0051] The head (magnetic recording and reproducing head) 15 of the magnetic disk device 1 is radially position-controlled by an actuator including a VCM 14 so as to stay on a track formed in the circumferential direction of the magnetic disk 10. Hereinafter, the above control is also referred to as positioning control.

[0052] If vibration, impact, etc. are applied from the outside to the actuator including the head and the magnetic disk device 1 equipped with the magnetic disk 10, the head 15 may write to the actual position deviating from the target position. In order to prevent the occurrence of the above deviation, the magnetic disk device 1 performs positioning control on the head 15 through a feedback loop. Hereinafter, the "deviation between the target position and the actual position" is also referred to as "positioning error".

[0053] If the positioning error based on the positioning control is large, the risk of erasing the data recorded on the adjacent tracks increases. Therefore, a threshold value (WOS: Write Offtrack Slice) is set for the positioning error. When the threshold value is exceeded, the writing operation is stopped, which has the function of preventing the erasure of the data recorded on the adjacent tracks. Hereinafter, the above threshold value is also referred to as "write off-track limit", "write off-track threshold", or "off-track limit".

[0054] Hereinafter, the writing process will be described with reference to the drawings.

[0055] Figure 2 This is a diagram showing an example of a write process of the magnetic disk device 1 according to the first embodiment. Figure 2 3 continuous tracks are shown, which are arranged in the order of track Trk0, track Trk1, and track Trk2 from the outer circumference along the radial direction of the disk 10. Figure 2 The upper, middle, and lower sections shown have data written in the order of track Trk1, track Trk2, and track Trk0, respectively.

[0056] like Figure 2 As shown in the upper part of , each data area of ​​the data written to the track Trk0 and the track Trk2 has an erase width EW. The data area D2 of the data written to the track Trk2 is written in a manner that is offset (offset) toward the track Trk1. In more detail, the data area D2 is located at a position that is offset by an error (positioning error, offset, or deviation from the track amount) PE2 toward the outer peripheral direction. The data area D0 of the data written to the track Trk0 is written in a manner that is offset toward the track Trk1. In more detail, the data area D0 is located at a position that is offset by an error PE0 toward the inner peripheral direction.

[0057] Since the data sectors on tracks Trk0 and Trk2 are written with the errors PE0 and PE2 offset as described above, the track width of the data area D1 of the data written to track Trk1 becomes the track width TW1 from the end of the inner circumference side of the data area D0 to the end of the outer circumference side of the data area D2. Here, when the inner circumference direction is set to positive, the track width TW1 is expressed by the following formula (1). In addition, TW1 represents the track width, TP represents the track pitch, EW represents the erase width, PE0 represents the error of the data area D0, and PE2 represents the error of the data area D2.

[0058] TW1=2TP-EW-(PE0-PE2)…(1)

[0059] Then, if Figure 2As shown in the middle section of , the case where the errors PE0 and PE2 in the data areas D0 and D2 are the upper limit value PEMX is described.

[0060] The upper limit value PEMX is the upper limit of the absolute value of the errors PE0 and PE2. When the track width TW1 at this time is set to the lower limit value TWL that can normally read user data, the lower limit value TWL is expressed by the following equation. In addition, TWL represents the lower limit value, and PEMX represents the upper limit value.

[0061] TWL=2TP-EW-2PEMX

[0062] According to the above formula, the TPI margin value TM is defined as twice the upper limit value PEMX. In addition, the TPI margin value TM is the track width narrowing (Track Squeeze) amount of the allowable read error rate. The TPI margin value TM is expressed by the following formula (2). In addition, TM represents the TPI margin value.

[0063] TM=2PEMX=2TP-EW-TWL…(2)

[0064] Based on the above-mentioned equations (1) and (2), the track width TW1 is expressed by the following equation (3).

[0065] TW1=TWL+TM-(PE0-PE2)…(3)

[0066] According to formula (3), the track width TW1 is determined by the lower limit value TWL, the TPI margin value TM, and the positioning errors PE0 and PE2 of the adjacent data. Furthermore, it can be seen that when the value obtained by subtracting the positioning error PE2 from the positioning error PE0 is less than the TPI margin value TM, the track width TW1 becomes greater than the lower limit value TWL. That is, when the difference between the positioning error PE0 and the positioning error PE2 is less than the TPI margin value TM, the user data written to the track Trk1 is preserved.

[0067] Then, if Figure 2 As shown in the lower part of FIG. 1 , when the positioning error PE2 is known, the case where the target position when writing to the track Trk0 is shifted by the correction amount OFS0 is described.

[0068] The relationship among the positioning error PE0, the correction amount OFS0, and the upper limit value PEMX can be expressed by the following equation: OFS0 represents the correction amount.

[0069] PE0≤OFS0+PEMX

[0070] Based on the above equation, equation (2), and equation (3), the track width TW1 is expressed by the following equation.

[0071] TW1 ≥ TWL + PEMX + (PE2 - OFS0)

[0072] Therefore, when the correction amount OFS0 is equal to the positioning error PE2, the track width TW1 is expressed by the following equation (4).

[0073] TW1≥TWL+PEMX…(4)

[0074] Formula (4) shows that when the correction amount OFS0 is set to the positioning error PE2, the track width TW1 is wider than the lower limit value TWL as the reading limit by the maximum positioning error (upper limit value) PEMX. However, this method does not take into account the writing to the track Trkm1 (refer to Figure 3 ) data protection.

[0075] Next, the processing when protecting the tracks Trk1 and Trkm1 adjacent to each other on both sides will be described.

[0076] Figure 3 FIG. 1 is a diagram showing an example of a write process of the magnetic disk device 1 according to the first embodiment. Figure 3 In the lower section, in addition to the three tracks Trk0, Trk1, and Trk2 recorded in the upper section, two tracks Trkm2 and Trkm1 are shown, and data is written in the order of track Trk1, track Trk2, track Trkm1, and track Trkm2.

[0077] like Figure 3 As shown in the lower part of FIG. 1 , data area D2 of track Trk2 is written with an error PE2 shifted toward the outer circumference, and data area Dm2 of track Trkm2 is written with an error PEm2 shifted toward the inner circumference. In track Trk0, data is written with the target position shifted by correction amount OFS0.

[0078] Here, the possible range of error PE0 when writing data to track Trk0 is expressed by the following equation (5).

[0079] OFS0-PEMX≤PE0≤OFS0+PEMX…(5)

[0080] At this time, the lower limit values ​​of the track width TW1 of the data area D1 and the lower limit values ​​of the track width TWm1 of the data area Dm1 are respectively expressed by the following equations (6a) and (6b). In addition, TWm1 is the track width of the data area Dm1.

[0081] TW1≥TWL+PEMX-(OFS0-PE2)…(6a)

[0082] TWm1≥TWL+PEMX+(OFS0-PEm2)…(6b)

[0083] The correction amount for the target position that can achieve a balance between the lower limit value of the track width TW1 and the lower limit value of the track width TWm1 is expressed by the following equation (7) by making the right side of equation (6a) equal to the right side of equation (6b).

[0084] OFS0=(PE2+PEm2) / 2…(7)

[0085] That is, the correction amount OFS is a value obtained by adding the positioning error PE of the sector two tracks inner from the target sector to half the value obtained by adding the positioning error PEm2 of the sector two tracks outer from the target sector.

[0086] Hereinafter, “positioning error” may be described as “error position”, and “correction amount” may be described as “target position”.

[0087] According to the above, by considering the positioning error (in one example, error PE2) of data written to a track located 2 tracks closer to the inner circumference (in one example, track Trk2) and the positioning error (in one example, error PEm2) of data written to a track located 2 tracks closer to the outer circumference (in one example, track Trkm2), the existing data on the adjacent tracks (in one example, tracks Trk1 and Trkm1) on both sides of the track to be written (in one example, track Trk0) can be protected under the same conditions. Thus, it is possible to prevent the situation where the width of either track becomes narrower and the preservation of user data decreases.

[0088] Next, a control configuration for calculating a target position will be described.

[0089] Figure 4 is a block diagram showing an example of a control structure of the magnetic disk device 1 according to the first embodiment, and shows Figure 1 The write processing circuit C1 of the write control unit 610 in FIG. Figure 4 In the address of the target sector (C, S), the header number is omitted, and only the cylinder number C and the sector number S are indicated. In addition, the cylinder number C is a number continuously added to the track on the disk 10 in the direction from the outer periphery to the inner periphery, or from the outer periphery to the inner periphery, and is sometimes called a track number.

[0090] like Figure 4As shown, the write processing circuit C1 of the write control unit 610 includes an off-track write table 611 , a target position track generation circuit 612 , a physical target position transducer 614 , a controller 615 , and an actuator 616 .

[0091] The target sector (C, S) is converted into a physical target position R (C, S) as the radial position of the disk 10 by the physical target position converter 614. The physical target position R (C, S) becomes the target position R1 (C, S) corrected by adding the correction amount OFS (C, S) of the target position. The difference between the physical position Y of the magnetic head 15 and the corrected target position R1 becomes the positioning error PE (C, S) in the sector (C, S). The positioning error PE is inputted as negative feedback to the controller 615 and outputted as the control amount U to the actuator 616. The actuator 616 outputs the physical position Y of the magnetic head 15 as the radial position of the disk 10 using the control amount U as input.

[0092] In addition, based on the address of the target sector (C, S), the positioning error PE (C+2, S) of the data area of ​​the data written to the sector (C+2, S) located 2 tracks from the inner circumference and the positioning error PE (C-2, S) of the data area of ​​the data written to the sector (C-2, S) located 2 tracks from the outer circumference are output with reference to the off-track write table 611. The positioning error PE (C+2, S) and the positioning error PE (C-2, S) are input to the target position track generation circuit 612, and the correction amount OFS (C, S) of the target position corresponding to the input is output.

[0093] As the correction amount OFS(C, S), for example, the following equation (8) can be obtained from equation (7).

[0094] OFS(C,S)=(PE(C+2,S)+PE(C-2,S)) / 2...(8)

[0095] Next, the structure of registering the positioning error in the off-track write table 611 is described.

[0096] Figure 5 This is a diagram showing an example of a control configuration of the magnetic disk device 1 according to the first embodiment. Figure 5 The structure for registering and updating the positioning error in the off-track write table 611 is shown.

[0097] like Figure 5 As shown, the positioning error PE (C, S) when writing to the target sector (C, S) is input to the absolute value circuit 617 and output as the absolute value PEA of the positioning error PE (C, S).

[0098] The absolute value PEA is compared with a predetermined registration determination threshold Th in the operational amplifier OP1. The operational amplifier OP1 outputs a registration flag RF1 as 1 when the absolute value PEA exceeds the registration determination threshold Th, and outputs a registration flag RF1 as 0 when the absolute value PEA does not exceed the registration determination threshold Th.

[0099] On the other hand, the off-track write table reference update block (hereinafter also referred to as OWT reference update block) 619 outputs the past maximum positioning error PEP in the target direction of the target address (in one example, sector (C, S)). The target direction is the same direction as the positioning error PE (C, S).

[0100] The operational amplifier OP2 compares the past maximum positioning error PEP with the absolute value PEA of the current positioning error PE(C, S), and outputs the update flag RF2 as 1 when the absolute value PEA exceeds the maximum positioning error PEP, and outputs the update flag RF2 as 0 when the absolute value PEA does not exceed the maximum positioning error PEP.

[0101] In addition, when there is no positioning error of the sector (C, S) in the OWT reference update block 619, the maximum positioning error PEP is output as 0, so the operational amplifier OP2 outputs the update flag RF2 as 1.

[0102] The operational amplifier OP3 outputs the flag DPE as 1 when the positioning error PE (C, S) is less than 0, and outputs the flag DPE as 0 when the positioning error PE (C, S) is not less than 0. That is, the sign of the positioning error PE (C, S) can be determined by using the flag DPE.

[0103] When the registration flag RF1 is output as 1 and the update flag RF2 is output as 1, the AND gate G1 outputs the update registration flag RF as 1. When the update registration flag RF is output as 1, the information corresponding to the sign of the positioning error PE (C, S) is updated or newly registered in the off-track write table 611.

[0104] Next, the target position correction amount OFS calculated by the target position trajectory generation circuit 612 will be described in detail.

[0105] Figure 6 It is a schematic diagram showing the correction amount OFS of the target position and the positioning error PE of the data written to the sector two tracks ahead. Figure 6 This is a diagram for explaining the operation of the target position track generating circuit 612 .

[0106] like Figure 6 As shown, the data of the positioning error PE (C-2, Si) is written from the target sector (C, Si) (i=1, 2, ..., 6) to the sector (C-2, Si) located 2 tracks away from the outer circumference, and the data of the positioning error PE (C+2, Si) is written from the target sector (C, S) to the sector (C+2, Si) located 2 tracks away from the inner circumference.

[0107] The positioning error PE(C-2, Si) and the positioning error PE(C+2, Si) can be referenced from the off-track write table 611. Figure 6 In the example shown, this is indicated by a black circle.

[0108] The correction amount OFS(C, Si) of the target position of the target sector (C, Si) is the target position correction amount calculated based on the information of the positioning error PE(C-2, Si) and the information of the positioning error PE(C+2, Si) in the off-track write table 611. Figure 6 In the example shown, the correction amount OFS(C, Si) is indicated by a white circle. In one example, the correction amount OFS(C, Si) of the target position is the midpoint between the positioning error PE(C-2, Si) and the positioning error PE(C+2, Si), and is generated for each sector.

[0109] As described above, since the correction amount OFS(C, Si) of the target position is generated, the respective user data on the unillustrated sectors (C-1, Si) and the sectors (C+1, Si) on the tracks represented by cylinder numbers C-1 and C+1 adjacent to the track represented by cylinder number C can be preserved.

[0110] In addition, Figure 6 In the example shown, the correction amount OFS(C, Si) is described as the midpoint between the positioning error PE(C-2, Si) and the positioning error PE(C+2, Si), but it is not limited to the midpoint. For example, in the case where the target position track along the center of the track is preferred, Figure 6 The correction amount OFS(C, Si) shown corrects the positioning target position between the center of the track.

[0111] In the magnetic disk device 1 that implements random access, the write state at the first two tracks of the target track varies. Therefore, generating the target position using the midpoint of the positioning error of the data written to the sector two tracks on the inner circumference and the positioning error of the data written to the sector two tracks on the outer circumference may not be optimal for the purpose of protecting the data of the sectors adjacent to the target sector.

[0112] Hereinafter, a case where the midpoint of the positioning error of the data written to the first two tracks is not used as the correction amount OFS of the target position will be described.

[0113] Figure 7 It is a schematic diagram showing the correction amount OFS of the target position and the positioning error PE of the data written to the sector two tracks ahead.

[0114] like Figure 7 As shown, the sectors (C-2, S4) and (C-2, S5) which are part of the 2 tracks on the outer side of the target sector (C, Si) and the sectors (C+2, S1), (C+2, S2), (C+2, S5), and (C+2, S6) which are part of the 2 tracks on the inner side of the target sector (C, Si) are in the recorded (registered) state (valid (active) state), and the positioning errors PE (C-2, S4), PE (C-2, S5), PE (C+2, S1), PE (C+2, S2), PE (C+2, S5), and PE (C+2, S6) in the above sectors are shown by black circles on the thick line TL.

[0115] exist Figure 7 In the example shown, sectors (C-2, S1), (C-2, S2), (C-2, S3), (C-2, S6), (C+2, S3), (C+2, S4) are in an unrecorded (unregistered) state, or sectors in which data was written at a time before (before) sectors (C-1, Si), (C+1, Si) of the first track not shown. Therefore, the above sectors will not affect sectors (C-1, Si) or sectors (C+1, Si), and are therefore determined to be in an invalid state, and the positioning error is regarded as 0.

[0116] Here, if we focus on the sectors (C, S1), (C, S2), (C, S6), the sectors (C-2, S1), (C-2, S2), (C-2, S6) on the two tracks on the outer circumference are in an ineffective state, and the sectors (C+2, S1), (C+2, S2), (C+2, S6) on the two tracks on the inner circumference are in an effective state. In other words, the sectors (C+1, S1), (C+1, S2), (C+1, S6) not shown in the figure are interfered by the sectors (C+2, S1), (C+2, S2), (C+2, S6), but the sectors (C-1, S1), (C-1, S2), (C-1, S6) not shown in the figure are not interfered by the sectors (C-2, S1), (C-2, S2), (C-2, S6).

[0117] At this time, by setting the correction amount OFS (C, S1), (C, S2), (C, S6) of the target position to a position closer to the outer side than the midpoint of the positioning error PE (C-2, S1), (C-2, S2), (C-2, S6) and the positioning error PE (C+2, S1), (C+2, S2), (C+2, S6), the preservation of data written to the sectors (C+1, S1), (C+1, S2), (C+1, S6) on the track adjacent to the inner side can be improved.

[0118] like Figure 7 As shown, the ratio of the length of line segments L1b, L2b, and L6b to the length of line segments L1a, L2a, and L6a is greater than 1. That is, line segment L1b is greater than line segment L1a, line segment L2b is greater than line segment L2a, and line segment L6b is greater than line segment L6a.

[0119] Next, if we focus on the sector (C, S4), the sector (C-2, S4) two tracks away from the outer circumference is in a valid state, and the sector (C+2, S4) two tracks away from the inner circumference is in an invalid state. That is, the sector (C-1, S4) not shown in the figure is interfered with by the sector (C-2, S4), but the sector (C+1, S4) not shown in the figure is not interfered with by the sector (C+2, S4).

[0120] At this time, by setting the correction amount OFS (C, S4) of the target position to a position closer to the inner side than the midpoint of the positioning error PE (C-2, S4) and the positioning error PE (C+2, S4), the data preservation of the sector (C-1, S4) on the track adjacent to the outer side can be improved.

[0121] like Figure 7 As illustrated in , the ratio of the length of line segment L4a to the length of line segment L4b is greater than 1.

[0122] In summary, by correcting the positioning target position of the target sector so as to be shifted toward the sector determined to be ineffective, the data preservation of the sectors adjacent to the target sector can be improved.

[0123] In the magnetic disk device 1 that performs random access, there is a case where positioning errors are written discontinuously on the same track. An example of discontinuous positioning errors will be described below.

[0124] Figure 8 It is a schematic diagram showing the correction amount OFS of the target position and the positioning error PE of the data written to the sector two tracks ahead.

[0125] like Figure 8As shown, in sector (C-2, S+i) (i=…, -2, -1, 0, 1, 2,…), a discontinuous positioning error is generated between sector (C-2, S) and sector (C-2, S+1), and in sector (C+2, S+i), a discontinuous positioning error is generated between sector (C+2, S) and sector (C+2, S+1).

[0126] In this case, discontinuity between the target sector (C, S) and the target sector (C, S+1) is caused between the correction amount OFS(C, S) and the correction amount OFS(C, S+1). Since the magnetic head 15 has mass and there is an upper limit to the current flowing in order to move the magnetic head 15, Figure 8 The head positioning control system cannot accurately follow the target position track as shown, and may damage the user data of the unillustrated sectors (C-1, S+1) and (C+1, S+1) on the tracks adjacent to the target sector (C, S+1) in the radial direction.

[0127] Reference Fig. 9 A modification of the first embodiment that can solve the above-mentioned problem will be described.

[0128] (Variation Example)

[0129] Fig. 9 It is a schematic diagram showing the correction amount OFS of the target position and the positioning error PE of the data written to the sector two tracks ahead.

[0130] In the description of the modified example, the target position correction amount OFS(C, S) in the equation (8) is referred to as a “target position correction amount initial value” or a “correction amount initial value”.

[0131] like Fig. 9 As shown, first, the auxiliary offset OFST (C, S) is obtained, which is the midpoint between the correction amount initial value OFS (C, S-1) of the sector (C, S-1) adjacent to the target sector (C, S) in the circumferential direction and the correction amount initial value OFS (C, S+1) of the sector (C, S+1). The auxiliary offset OFST (C, S) is expressed by the following equation (9).

[0132] OFST(C,S)=(OFS(C,S-1)+OFS(C,S+1)) / 2...(9)

[0133] That is, the auxiliary offset amount OFST(C, S) is a value half of the value obtained by adding the correction amount initial value OFS(C, S+1) to the correction amount initial value OFS(C, S-1).

[0134] Next, the optimal correction value OFSR(C, S) of the target position as the midpoint between the initial correction value OFS(C, S) of the sector (C, S) and the auxiliary offset OFST(C, S) is obtained. The optimal correction value OFSR(C, S) is expressed by the following equation (10).

[0135] OFSR(C,S)=(OFS(C,S)+OFST(C,S)) / 2...(10)

[0136] In one example, the correction amount optimum value OFSR(C, S) is a half of the value obtained by adding the auxiliary offset OFST(C, S) to the correction amount initial value OFS(C, S).

[0137] The magnetic disk device 1 according to the modified example can correct the correction amount initial value OFS(C, S) to the correction amount optimal value OFSR(C, S) which corresponds discontinuously in the above-mentioned steps.

[0138] In summary, the magnetic disk device 1 is capable of calculating the initial correction values ​​OFS(C, S-1) and OFS(C, S+1) of a pair of sectors (C, S-1) and (C, S+1) adjacent to the target sector (C, S) in the circumferential direction, calculating the auxiliary offset OFST(C, S) which is the midpoint of the initial correction values ​​OFS(C, S-1) and OFS(C, S+1) of the pair of sectors (C, S-1) and (C, S+1), and calculating the optimal correction value OFSR(C, S) which is the midpoint between the initial correction value OFS(C, S) and the auxiliary offset OFST(C, S).

[0139] The correction amount OFSR is not limited to the midpoint between the correction amount initial value OFS(C, S) and the auxiliary offset amount OFST(C, S), and may be, for example, between the midpoint and the correction amount initial value OFS(C, S).

[0140] Likewise, the correction amount initial value OFS(C, S+1) can also be corrected to the correction amount optimal value OFSR(C, S+1).

[0141] By correcting the initial correction value OFS(C, S) to the optimal correction value OFSR(C, S) as described above, it is possible to generate an optimal target position correction amount that alleviates the discontinuity of the target position correction amount caused by the discontinuity of the positioning error of the data written to the sector of the first two tracks.

[0142] Furthermore, when equation (10) is substituted into equation (9), the optimal correction value OFSR(C, S) is expressed by the following equation (11).

[0143] OFSR(C,S)=OFS(C,S) / 2+OFS(C,S-1) / 4+OFS(C,S+1) / 4…(11)

[0144] According to formula (11), the optimal correction value OFSR (C, S) is a weighted moving average of the initial correction values ​​OFS (C, S-1), OFS (C, S), and OFS (C, S+1) of three consecutive sectors (C, S-1), (C, S), and (C, S+1). If it is generalized, the optimal correction value OFSR (C, S) is expressed by the following formula (12).

[0145]

[0146] In one example, the weighting coefficient ai decreases as the distance from the target sector (C, S) increases. As shown in equation (11), it is 1 / 2 when i=0 and 1 / 4 when i=+1 or -1.

[0147] The correction amount optimum value OFSR may be calculated by calculating the correction amount initial values ​​OFS for a plurality of sectors and linearly combining the plurality of correction amount initial values ​​OFS using equation (12).

[0148] More specifically, calculate the initial value OFS of the correction amount for sectors from the target sector to a predetermined number in front (on one side in the circumferential direction) and the initial value OFS of the correction amount for sectors from the target sector to a predetermined number in the back (on the other side in the circumferential direction), and then linearly combine the multiple initial value OFS of the correction amount using formula (12).

[0149] like Fig. 9 As shown in the example, the initial correction value OFS(C, S-2), (C, S-1), (C, S), (C, S+1), (C, S+2) can be calculated for sectors (C, S-2), (C, S-1), (C, S), (C, S+1), (C, S+2), respectively, and the optimal correction value OFSR(C, S) can be calculated using formula (12).

[0150] The effects of the first embodiment will be described.

[0151] According to the magnetic disk device 1 involved in the first embodiment, when writing data to the first sector (in one example, the sector (C, S)), the magnetic disk device 1 corrects the positioning target position of the first sector based on the positioning error of the second sector (in one example, the sectors (C-2, S), (C+2, S)) located two tracks before the first sector in the radial direction. Therefore, it is possible to generate a dynamic positioning target position based on the positioning error of the second sector, protect the data on the tracks adjacent to the first sector, and average the excess rate of the off-track limit. As a result, it is possible to obtain a magnetic disk device 1 and a control method for the magnetic disk device 1 that can prevent the quality of adjacent tracks from deteriorating without reducing the write performance due to an increase in the frequency of stoppage of the write action caused by the excess detection of the off-track limit as described later.

[0152] Normally, the magnetic disk device 1 includes a write off-track processing circuit, and stops the writing operation when it is determined that the absolute value of the positioning error PE exceeds the write off-track limit absolute value WOS before writing data to the target sector.

[0153] However, since the positioning error PE is detected by sampling processing, there is a case where it exceeds the off-track limit WOS and is written. Fig.10 The sampling process will be described.

[0154] Fig.10 is a schematic diagram for explaining an example of sampling processing. Fig.10 , in addition to the trajectory of the positioning error PE of the magnetic head 15 shown by the solid curve and the dashed curve, the open and closed state of the write gate WG is also shown. In addition, PE1, PE2, ..., PE7 represented by white circles show the positioning errors PE intermittently detected by the sampling process.

[0155] like Fig.10 As shown, in the magnetic disk device 1, the positioning error PE is detected at predetermined time intervals T by sampling processing. Fig.10 In the example shown, the positioning errors PE1, PE2, PE3, PE4 are located within the off-track limit ±WOS, and the positioning error PE5 is located outside the off-track limit ±WOS.

[0156] After detecting the positioning error PE5, the magnetic disk device 1 (write control unit 610) turns off the write gate WG. Therefore, data exceeding the positioning error PE5 of the off-track limit ±WOS is written into the sector.

[0157] In summary, when the positioning error PE is detected by sampling, a delay time is generated from when the physical position of the magnetic head 15 exceeds the off-track limit ±WOS until it is detected, and the writing operation is continued. The excess amount from the off-track limit ±WOS at this time is called the overrun amount OVR.

[0158] When the absolute value of the maximum value of the overrun amount OVR is set to the overrun maximum absolute value OVMX, the upper limit value PEMX of the absolute value of the positioning error is the sum of the absolute value of the deviation from the track limit WOS and the absolute value of the overrun maximum OVMX, as expressed by equation (13). In addition, PEMX represents the maximum value of the absolute value of the positioning error, WOS represents the absolute value of the deviation from the track limit, and OVMX represents the absolute value of the overrun maximum.

[0159] PEMX=WOS+OVMX…(13)

[0160] In addition, based on the formula (2), the TPI margin value TM is expressed by the following formula (14).

[0161] TM=2(WOS+OVMX)…(14)

[0162] Hereinafter, a magnetic disk device 1 according to a second embodiment of the present invention is described, in which the correction amount OFS of the target position is determined by taking into account the deviation from the track limit absolute value WOS. In addition, in the second embodiment described below, the same reference numerals are used for the same parts as those in the first embodiment described above, and the detailed description thereof is omitted or simplified, and the description is centered on the parts different from the first embodiment.

[0163] (Second embodiment)

[0164] Fig.11 This is a diagram showing an example of a write process of the magnetic disk device 1 according to the second embodiment. Fig.11 The upper part is Figure 2 The middle section is a schematic diagram represented by the absolute value of the deviation from the track limit WOS and the absolute value of exceeding the maximum value OVMX.

[0165] like Fig.11 As shown in the upper part of FIG. 1 , predetermined (predetermined) off-track limits ±WOS are set in tracks Trk0, Trk1, and Trk2. The off-track limit on the outer circumference side is -WOS, and the off-track limit on the inner circumference side is +WOS.

[0166] The positioning error of the data area D2 of the data written in the track Trk2 is the maximum value in the peripheral direction and is expressed by the following equation.

[0167] -PEMX=-WOS-OVMX

[0168] The positioning error of the data area D0 of the data written in the track Trk0 is the maximum value in the inner circumference direction and is expressed by the following equation.

[0169] +PEMX=+WOS+OVMX

[0170] At this time, the track pitch TP is determined so that the track width of the track Trk1 becomes the lower limit value TWL, and the track pitch TP is expressed by the following formula (15).

[0171] 2TP=EW+TWL+2(WOS+OVMX)…(15)

[0172] Fig.11 The middle section shows the case where the positioning error PE2 of the track Trk2 is known and the positioning error PE2 does not exceed the off-track limit -WOS on the outer peripheral side.

[0173] At this time, when data is written to track Trk0 and the positioning error PE0 of the data area D0 is a value exceeding the maximum value OVMX from the off-track limit +WOS on the inner circumference side, the positioning error PE0 is expressed by the following formula.

[0174] PE0=+WOS+OVMX=+PEMX

[0175] At this time, the track width TW1 of the track Trk1 is expressed by the following equation based on equation (3) and equation (14).

[0176] TW1=TWL+(WOS+OVMX)+PE2

[0177] Here, the positioning error PE2 satisfies the following conditions.

[0178] PE2>-WOS

[0179] Therefore, the track width TW1 is expressed by the following equation.

[0180] TW1>TWL+OVMX

[0181] According to the above formula, it is possible to ensure that the track width TW1 has a margin exceeding the maximum absolute value OVMX with respect to the lower limit value TWL of the track width.

[0182] Fig.11 The lower part of shows the case where the positioning error PE2 at the track Trk2 is known and the positioning error PE2 exceeds the off-track limit -WOS on the outer peripheral side.

[0183] At this time, the overrun amount OVR2 of the data area D2 is expressed by the following equation.

[0184] OVR2=PE2+WOS

[0185] Here, a new off-track limit WOS0p on the inner circumference side of the track Trk0 is generated by shifting the off-track limit on the inner circumference side from +WOS by OVR2. The off-track limit WOS0p is represented by the following equation.

[0186] WOS0p=2WOS+PE2…(16)

[0187] Here, when the positioning error PE0 of the data area D0 of the data written to the track Trk0 exceeds the new inner side off-track limit WOS0p by exceeding the maximum absolute value OVMX on the inner side, the positioning error PE0 is expressed by the following formula.

[0188] PE0=WOS0p+OVMX

[0189] If the above equations, equation (3), and equation (14) are considered, the track width TW1 is expressed by the following equation (17).

[0190] TW1=TWL+OVMX…(17)

[0191] According to formula (17), it is possible to ensure that the track width TW1 has a margin exceeding the maximum absolute value OVMX relative to the lower limit value TWL of the track width.

[0192] According to the above content, when the positioning error PE2 of track Trk2 two tracks on the inner side of track Trk0 is known, the deviation track limit WOS0p on the inner side of track Trk0 is set based on the positioning error PE2, so that the track width of track Trk1 adjacent to the inner side can ensure a margin exceeding the maximum absolute value OVMX relative to the lower limit value TWL.

[0193] However, the absolute value of the new inner-side off-track limit WOS0p of track Trk0 is less than the absolute value of the original inner-side off-track limit + WOS, and satisfies the following formula.

[0194] |WOS0p|≤|+WOS|

[0195] That is, the new inner side off-track limit WOS0p is formed by narrowing the original inner side off-track limit +WOS, so the inner side off-track occurrence rate becomes high, which may reduce the writing performance.

[0196] Therefore, the positioning target position offset correction amount OFS0 of track Trk0 is balanced in such a way that the probability of exceeding the outer circumference side of track Trk0 by the off-track limit -WOS is consistent with the probability of exceeding the new inner circumference side of the off-track limit WOS0p. That is, the target position offset correction amount OFS0 satisfies the following formula.

[0197] OFS0-(-WOS)=WOS0p-OFS0

[0198] That is, the correction amount OFS0 is expressed by the following equation (18).

[0199] OFS0=(WOS0p-WOS) / 2…(18)

[0200] Furthermore, consider a case where the off-track limit -WOS on the outer circumference side of track Trk0 changes due to a positioning error in the inner circumference direction at track Trkm2 which is two tracks on the outer circumference side of track Trk0.

[0201] Below, refer to Fig.12 , the correction amount OFS0 when the off-track limit -WOS on the outer circumference side of the track Trk0 and the off-track limit +WOS on the inner circumference side are changed is described.

[0202] like Fig.12 As shown, the positioning error PEm2 of the track Trkm2 is known and the positioning error PEm2 exceeds the off-track limit +WOS on the inner circumference side.

[0203] At this time, the overrun amount OVRm2 is expressed by the following equation.

[0204] OVRm2=PEm2-WOS

[0205] Here, a new off-track limit WOS0m on the outer circumference side is generated by shifting the off-track limit on the outer circumference side of the track Trk0 from -WOS by OVRm2.

[0206] WOS0m=-WOS+OVRm2

[0207] That is, the off-track limit WOS0m is expressed by the following equation (19).

[0208] WOS0m=-2WOS+PEm2…(19)

[0209] At this time, a balance is achieved so that the probability of the inner side off-track limit WOS0p exceeding the track Trk0 on the inner side is consistent with the probability of the outer side off-track limit WOS0m exceeding the outer side. That is, the target position is offset by a correction amount OFS0 that satisfies the following equation.

[0210] OFS0-WOS0m=WOS0p-OFS0

[0211] That is, the correction amount OFS0 is expressed by the following equation (20).

[0212] OFS0=(WOS0p+WOS0m) / 2…(20)

[0213] Next, a control configuration for calculating a target position will be described.

[0214] Fig.13 is a block diagram showing an example of a control structure of the magnetic disk device 1 according to the second embodiment, showing Figure 1 The write processing circuit C1 of the write control unit 610.

[0215] like Fig.13 As shown, the write processing circuit C1 of the write control unit 610 includes a compaction processing circuit 613, operational amplifiers OP4, OP5, and an OR gate G2. Information on the positioning error PE (C+2, S) of data written to two tracks on the inner side of the target sector (C, S), information on the positioning error PE (C-2, S) of data written to two tracks on the outer side of the target sector (C, S), a predetermined TPI margin value TM, and a predetermined write off-track limit absolute value WOS that does not depend on the sector are input to the compaction processing circuit 613. The compaction processing circuit 613 outputs the off-track limits WOSp and WOSm corresponding to these inputs to the operational amplifiers OP4, OP5.

[0216] Here, the off-track limit WOSp on the inner circumference side is +WOS, which is a predetermined value, when the positioning error PE(C+2, S) of the data of the sector (C+2, S) two tracks closer to the inner circumference side does not exceed the predetermined write off-track limit -WOS on the outer circumference side on the outer circumference side. If it exceeds, equation (16) is applied. That is, the off-track limit WOSp on the inner circumference side is expressed by the following equation.

[0217] WOSp=+WOS(PE(C+2,S)≥-WOS)

[0218] WOSp=2WOS+PE(C+2,S)(PE(C+2,S)<-WOS)

[0219] In addition, when the positioning error PE(C-2, S) of the data of the sector (C-2, S) two tracks away from the outer circumference does not exceed the predetermined off-track limit +WOS on the inner circumference, the off-track limit WOSm on the outer circumference is -WOS, which is a predetermined value. If it exceeds, equation (19) is applied. That is, the off-track limit WOSm on the outer circumference is expressed by the following equation.

[0220] WOSm=-WOS(PE(C-2,S)≤+WOS)

[0221] WOSm=-2WOS+PE(C-2,S)(PE(C-2,S)>+WOS)

[0222] The positioning error PE(C, S) of the target sector (C, S) is compared with the off-track limit WOSp on the inner circumference side in the operational amplifier OP4, and is compared with the off-track limit WOSm on the outer circumference side in the operational amplifier OP5. When the positioning error PE(C, S) exceeds either the off-track limit WOSp or the off-track limit WOSm, a write inhibit flag WINH is output from the OR gate G2. After receiving the write inhibit flag WINH, the system controller 130 stops the write operation.

[0223] Through the above-mentioned actions, it is possible to ensure that the track widths of the sectors (C+1, S) and (C-1, S) adjacent to the target sector (C, S) are greater than the lower limit value TWL.

[0224] On the other hand, the compression processing circuit 613 also outputs the off-track limits WOSp and WOSm to the target position track generation circuit 612. The target position track generation circuit 612 performs the operation of equation (20) based on the input off-track limits WOSp and WOSm. The target position track generation circuit 612 outputs the correction amount OFS(C, S) of the target position obtained by the operation. The output correction amount OFS(C, S) is added to the physical target position R(C, S) to become the target position R1(C, S). The target position R1(C, S) is input to the differentiator.

[0225] Next, the target position correction amount OFS calculated by the target position trajectory generation circuit 612 will be described in detail.

[0226] Fig.14 It is a schematic diagram showing the correction amount OFS of the target position, the positioning error PE of the data written to the sector two tracks before, and the off-track limits WOSp and WOSm with respect to the target sector.

[0227] like Fig.14As shown, the data of the positioning error PE (C-2, Si) is written to the sector (C-2, Si) located 2 tracks on the outer side from the target sector (C, Si) (i=1, 2, ..., 8), and the data of the positioning error PE (C+2, Si) is written to the sector (C+2, Si) located 2 tracks on the inner side from the target sector (C, S).

[0228] The positioning error PE(C-2, Si) and the positioning error PE(C+2, Si) can be referenced from the off-track write table 611. Fig.14 In the example shown, this is indicated by a black circle.

[0229] The correction amount OFS(C, Si) of the target position of the target sector (C, Si) is Fig.14 This is indicated by a white circle in the example shown.

[0230] The off-track limit WOSp on the inner circumference side and the off-track limit WOSp on the outer circumference side relative to the target sector (C, S) are Fig.14 This is indicated by a dashed line in the example shown.

[0231] First, the correction amount OFS(C, Si) based on the off-track limits WOSm(C, Si) and WOSp(C, Si) when writing to the target sectors (C, S1), (C, S2), (C, S4), (C, S5), (C, S7), and (C, S8) is explained.

[0232] The positioning errors PE(C-2, S1), PE(C-2, S2), PE(C-2, S4), PE(C-2, S5), PE(C-2, S7), and PE(C-2, S8) of the data when writing to the sectors 2 tracks on the outer circumference side of the above-mentioned target sector do not exceed the predetermined inner circumference side off-track limit +WOS in the inner circumference direction. Therefore, the outer circumference side off-track limits WOSm(C, S1), WOSm(C, S2), WOSm(C, S4), WOSm(C, S5), WOSm(C, S7), and WOSm(C, S8) when writing to the target sectors (C, S1), (C, S2), (C, S4), (C, S5), (C, S7), and (C, S8) all become predetermined values ​​of -WOS.

[0233] In addition, the positioning errors PE(C+2, S1), PE(C+2, S2), PE(C+2, S4), PE(C+2, S5), PE(C+2, S7), and PE(C+2, S8) of the data when writing to the sectors 2 tracks on the inner side of the target sector do not exceed the predetermined outer side off-track limit -WOS in the outer direction. Therefore, the inner side off-track limits WOSp(C, S1), WOSp(C, S2), WOSp(C, S4), WOSp(C, S5), WOSp(C, S7), and WOSp(C, S8) when writing to the target sectors (C, S1), (C, S2), (C, S4), (C, S5), (C, S7), and (C, S8) all become the predetermined value +WOS.

[0234] Based on the above, the target position correction amounts OFS (C, S1), OFS (C, S2), OFS (C, S4), OFS (C, S5), OFS (C, S7), and OFS (C, S8) all become zero.

[0235] Next, the correction amount OFS(C, Si) based on the off-track limits WOSm(C, Si) and WOSp(C, Si) when writing to the target sector (C, S3) is described.

[0236] When writing to a sector (C-2, S3) two tracks away from the outer circumference of the target sector (C, S3), the positioning error PE(C-2, S3) exceeds the predetermined inner circumference side off-track limit +WOS in the inner circumference direction. More specifically, the positioning error PE(C-2, S3) exceeds the inner circumference side off-track limit +WOS by the overrun amount OVR(C-2, S3).

[0237] In addition, the overrun amount OVR(C-2, S3) is expressed by the following equation.

[0238] OVR(C-2,S3)=PE(C-2,S3)-WOS

[0239] The off-track limit WOSm(C, S3) on the outer side when writing to the target sector (C, S3) is a value that is offset from the predetermined value -WOS by the excess amount OVR(C-2, S3), and is therefore represented by the following formula.

[0240] WOSm(C,S3)=-2WOS+PE(C-2,S3)

[0241] On the other hand, when writing to the sector (C+2, S3) two tracks inner of the target sector (C, S3), the positioning error PE(C+2, S3) exceeds the predetermined outer side off-track limit -WOS in the outer direction. More specifically, the positioning error PE(C+2, S3) exceeds the off-track limit -WOS in the outer direction by the overrun amount OVR(C+2, S3).

[0242] In addition, the overrun amount OVR(C+2, S3) is expressed by the following equation.

[0243] OVR(C+2,S3)=PE(C+2,S3)+WOS

[0244] The inner side off-track limit WOSp(C, S3) is a value obtained by shifting from a predetermined value +WOS by an excess amount OVR(C+2, S3), and is therefore represented by the following equation.

[0245] WOSp(C,S3)=+2WOS+PE(C+2,S3)

[0246] The target position correction amount OFS(C, S3) is the midpoint between the off-track limit WOSm(C, S3) on the outer circumference side and the off-track limit WOSp(C, S3) on the inner circumference side, and is therefore represented by the following equation.

[0247] OFS (C, S3) = (WOSp (C, S3) + WOSm (C, S3)) / 2

[0248] From the above-mentioned equation, the correction amount OFS(C, S3) can also be expressed by the following equation using the positioning errors PE(C+2, S3) and PE(C-2, S3).

[0249] OFS(C,S3)=(PE(C+2,S3)+PE(C-2,S3)) / 2

[0250] Next, the correction amount OFS(C, Si) based on the off-track limits WOSm(C, Si) and WOSp(C, Si) when writing to the target sector (C, S6) is described.

[0251] When writing to a sector (C-2, S6) two tracks outside the target sector (C, S6), the positioning error PE(C-2, S6) exceeds the predetermined inner side off-track limit +WOS. More specifically, the positioning error PE(C-2, S6) exceeds the inner side off-track limit +WOS by an overrun amount OVR(C-2, S6).

[0252] In addition, the overrun amount OVR(C-2, S6) is expressed by the following equation.

[0253] OVR(C-2,S6)=PE(C-2,S6)-WOS

[0254] The off-track limit WOSm(C, S6) on the outer circumference side is a value obtained by shifting from a predetermined value -WOS by an excess amount OVR(C-2, S6), and is therefore represented by the following equation.

[0255] WOSm(C,S6)=-2WOS+PE(C-2,S6)

[0256] On the other hand, the positioning error PE(C+2, S6) when writing to the sector (C+2, S6) two tracks inner of the target sector (C, S6) does not exceed the predetermined outer off-track limit -WOS. Therefore, the inner off-track limit WOSp(C, S6) becomes the predetermined value +WOS.

[0257] The target position correction amount OFS(C, S6) is the midpoint between the off-track limit WOSm(C, S6) on the outer circumference side and the off-track limit WOSp(C, S6) on the inner circumference side, and is therefore represented by the following equation.

[0258] OFS(C, S6)=(WOSm(C, S6)+WOS) / 2

[0259] From the above-mentioned equation, the correction amount OFS(C, S6) can also be expressed by the following equation using the positioning error PE(C-2, S6).

[0260] OFS(C,S6)=(-WOS+PE(C-2,S6)) / 2

[0261] The effects of the second embodiment will be described.

[0262] According to the magnetic disk device 1 involved in the second embodiment, the magnetic disk device 1 corrects the positioning target position of the target sector based on the threshold value (off-track limit WOSp, WOSm) determined based on the positioning error of the sector 2 tracks ahead of the target sector. Therefore, the dynamic movement of the target position can be obtained in the same manner as in the first embodiment, and the same effect as in the first embodiment can be obtained.

[0263] In the second embodiment, similarly to the modification of the first embodiment, the correction amount initial value OFS may be corrected to the correction amount optimal value OFSR that can cope with the discontinuous positioning error. The modification of the second embodiment will be described below.

[0264] (Variation Example)

[0265] Fig.15It is a schematic diagram showing the correction amount OFS of the target position and the off-track limits WOSp and WOSm with respect to the target sector.

[0266] like Fig.15 As shown, the inner side off-track limit WOSp(C, S) and the inner side off-track limit WOSp(C, S+1) are discontinuous, and the outer side off-track limit WOSm(C, S) and the outer side off-track limit WOSm(C, S+1) are discontinuous.

[0267] When discontinuous positioning errors occur in the unillustrated sectors (C-2, S) and (C-2, S+1), and when discontinuous positioning errors occur in the unillustrated sectors (C+2, S) and (C+2, S+1), the discontinuous inner side off-track limits WOSp(C, S), WOSp(C, S+1) and the outer side off-track limits WOSm(C, S), WOSm(C, S+1) described above are obtained.

[0268] The trajectory of the correction amount initial values ​​OFS(C, S) and OFS(C, S+1) based on the target position determined by the midpoint of the above-mentioned off-track limit has a sharp change. In addition, the correction amount initial value OFS(C, S) is expressed by the following formula.

[0269] OFS(C,S)=(WOSp(C,S)+WOSm(C,S)) / 2

[0270] exist Fig.15 In the state shown, similarly to the modification of the first embodiment, the auxiliary offset amount OFST(C, S) is calculated from the correction amount initial values ​​OFS(C, S-1) and OFS(C, S+1) of the sectors (C, S-1) and (C, S+1) adjacent to the target sector (C, S) in the circumferential direction, and the correction amount optimal value OFSR(C, S) is calculated from the correction amount initial value OFS(C, S) and the auxiliary offset amount OFST(C, S). The auxiliary offset amount OFST(C, S) and the correction amount optimal value OFSR(C, S) are expressed by the following equations.

[0271] OFST(C,S)=(OFS(C,S-1)+OFS(C,S+1)) / 2

[0272] OFSR(C,S)=(OFS(C,S)+OFST(C,S)) / 2

[0273] The optimal correction value OFSR (C, S+1) of the target sector (C, S+1) can also be calculated by the same steps. By correcting the initial correction value OFS to the optimal correction value OFSR as described above, even if the positioning error of the data written to the first two tracks is discontinuous, the data written to the radially adjacent sectors (in one example, sectors (C-1, Si), (C+1, Si)) can be protected.

[0274] In addition, equation (11) and equation (12) can also be applied in the same manner.

[0275] Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and / or their variations are included in the scope and gist of the invention, and are included in the invention described in the claims and the scope of their equivalents. It is also possible to combine multiple embodiments as needed.

Claims

1. A magnetic disk device comprising: disk; A magnetic head is positioned at a track of the magnetic disk arranged at a predetermined track pitch, and writes data to the track and reads data from the track; as well as A controller having an off-track write table is used to position the magnetic head, and an address in the magnetic track where data is written and a positioning error of the magnetic head relative to the magnetic track at the address are registered in the off-track write table. When writing data to the first sector, the controller corrects a positioning target position of the first sector based on a positioning error of a second sector located two tracks before the first sector in a radial direction.

2. The magnetic disk device according to claim 1, When the second sector is unregistered or data is written to the second sector before data is written to a sector between the first sector and the second sector, the controller determines that the second sector is in an invalid state and sets the positioning error of the second sector to zero.

3. The magnetic disk device according to claim 1, The controller corrects the positioning target position of the first sector based on the positioning error of the third sector located two tracks inner than the first sector and the positioning error of the fourth sector located two tracks outer than the first sector.

4. The magnetic disk device according to claim 3, The controller corrects the positioning target position of the first sector based on a correction amount that is a half of a value obtained by adding the positioning error of the third sector to the positioning error of the fourth sector.

5. The magnetic disk device according to claim 4, the controller, When the third sector is in an unregistered state or data is written to the third sector before data is written to a sector between the first sector and the third sector, the third sector is judged to be in an invalid state, and the positioning error of the third sector is set to 0. When the fourth sector is in an unregistered state or data is written to the fourth sector before data is written to a sector between the first sector and the fourth sector, the fourth sector is judged to be in an invalid state, and the positioning error of the fourth sector is set to 0. When the third sector or the fourth sector is in an ineffective state, the positioning target position of the first sector is corrected in such a manner that it is offset toward the sector judged to be in an ineffective state among the third sector and the fourth sector, compared with the positioning target position corrected based on the correction amount.

6. The magnetic disk device according to claim 4, the controller, For a pair of sectors adjacent to the first sector in a circumferential direction orthogonal to the radial direction, an initial correction value is calculated, the initial correction value being half of a value obtained by adding a positioning error of a sector located two tracks inner from the pair of sectors to a positioning error of a sector located two tracks outer from the pair of sectors, calculating an auxiliary offset amount which is a value obtained by adding an initial correction amount of one sector of the pair of sectors to an initial correction amount of the other sector of the pair of sectors, calculating an optimum correction amount value, the optimum correction amount value being a value obtained by adding the auxiliary offset amount to the correction amount, and Based on the optimal correction amount value, the positioning target position of the first sector is corrected.

7. The magnetic disk device according to claim 4, For a predetermined number of sectors arranged in a first direction from the first sector in a circumferential direction orthogonal to the radial direction and a predetermined number of sectors located in a second direction opposite to the first direction from the first sector, an initial correction value is calculated, the initial correction value being half of a value obtained by adding a positioning error of a sector on two tracks on the inner circumference side to a positioning error of a sector on two tracks on the outer circumference side, Calculate the optimal correction value by using the correction value initial value in the predetermined number of sectors and the linear combination of the correction value, Based on the optimal correction amount value, the positioning target position of the first sector is corrected.

8. The magnetic disk device according to claim 3, the controller, calculating a threshold for determining whether to stop the writing operation to the first sector based on the positioning error of the third sector and the positioning error of the fourth sector, Based on the threshold, the positioning target position of the first sector is corrected.

9. A control method for a magnetic disk device, the magnetic disk device comprising a magnetic disk, a magnetic head, and an off-track writing table, the magnetic head being positioned at a track of the magnetic disk arranged at a predetermined track pitch, writing data to the track, and reading data from the track, The control method comprises: Positioning the magnetic head; registering an address in the track where data is written and a positioning error of the magnetic head relative to the track at the address in the off-track writing table; as well as When writing data to the first sector, the positioning target position of the first sector is corrected based on the positioning error of the second sector located two tracks before the first sector in the radial direction.

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