Magnetic disk device and control method for magnetic disk device

Abstract

To provide a magnetic disk device capable of preventing degradation of adjacent track quality without degrading write performance.SOLUTION: A magnetic disk device including: a magnetic disk; a magnetic head; and a controller having an off-track write table, positioning the magnetic head, and registering an address in which data in the track is written, and positioning errors for the track of the magnetic head at the address in the off-track write table. The controller corrects a positioning target position of a first sector based on the positioning error of a second sector located two tracks ahead of the first sector in a radial direction when writing data to the first sector.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a magnetic disk device and a method for controlling the magnetic disk device. [Background technology]

[0002] A magnetic disk device includes a magnetic disk, a magnetic head for writing / reading data to / from the magnetic disk, a system controller, and the like. The system controller controls the positioning of the magnetic head relative to a number of tracks formed on the magnetic disk in an approximately concentric pattern (hereinafter also referred to as "positioning"). The magnetic head is positioned off-track in the radial direction of the magnetic disk relative to the tracks due to positioning control errors. If the amount of off-track is large, there is a high risk of erasing data recorded on adjacent tracks. If writing is stopped at a small amount of off-track to avoid erasing data, writing performance will decrease. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 1,137,3684 [Patent Document 2] U.S. Patent No. 7,245,447 [Patent Document 3] U.S. Patent No. 9,892,749 Summary of the Invention [Problem to be solved by the invention]

[0004] The present embodiment aims to provide a magnetic disk device and a method for controlling the magnetic disk device that can prevent deterioration of the quality of adjacent tracks without deteriorating the write performance. [Means for solving the problem]

[0005] A magnetic disk device according to one embodiment comprises a magnetic disk, a magnetic head which is positioned on a track on the magnetic disk at a predetermined track pitch to write data to the track and read data from the track, and a controller having an off-track write table, which positions the magnetic head and registers in the off-track write table an address at which data is written on the track and a positioning error of the magnetic head relative to the track at the address, and when writing data to a first sector, the controller corrects a positioning target position of the first sector based on a positioning error of a second sector which is located two tracks radially away from the first sector.

[0006] A method for controlling a magnetic disk device according to one embodiment is a method for controlling a magnetic disk device including a magnetic disk, a magnetic head that is positioned on a track on the magnetic disk at a predetermined track pitch, writes data to the track, and reads data from the track, and an off-track write table, the method comprising the steps of: The magnetic head is positioned, and the address at which data is written on the track and the positioning error of the magnetic head relative to the track at that address are registered in the off-track write table, and when data is written to a first sector, the positioning target position of the first sector is corrected based on the positioning error of a second sector located two tracks away from the first sector in the radial direction. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram showing the configuration of a magnetic disk device according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a write process of the magnetic disk device according to the first embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of a write process of the magnetic disk device according to the first embodiment. [Figure 4]FIG. 4 is a block diagram showing an example of a control configuration of the magnetic disk device according to the first embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of a control configuration of the magnetic disk device according to the first embodiment. [Figure 6] FIG. 6 is a schematic diagram showing the correction amount of the target position and the positioning error of the data written in the sector two tracks ahead. [Figure 7] FIG. 7 is a schematic diagram showing the correction amount of the target position and the positioning error of the data written in the sector two tracks ahead. [Figure 8] FIG. 8 is a schematic diagram showing the correction amount of the target position and the positioning error of the data written in the sector two tracks ahead. [Figure 9] FIG. 9 is a schematic diagram showing the correction amount of the target position and the positioning error of the data written in the sector two tracks ahead. [Figure 10] FIG. 10 is a schematic diagram for explaining an example of the sampling process. [Figure 11] FIG. 11 is a diagram showing an example of a write process of the magnetic disk device according to the second embodiment. [Figure 12] FIG. 12 is a diagram showing an example of a write process of the magnetic disk device according to the second embodiment. [Figure 13] FIG. 13 is a block diagram showing an example of a control configuration of the magnetic disk device according to the second embodiment. [Figure 14] FIG. 14 is a schematic diagram showing the correction amount of the target position, the positioning error of the data written in the sector two tracks ahead, and the off-track slice with respect to the target sector. [Figure 15] FIG. 15 is a schematic diagram showing the correction amount of the target position and the off-track slice for the target sector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment will be described with reference to the drawings. Note that the drawings are merely examples and do not limit the scope of the invention. FIG. 1 is a block diagram showing the configuration of a magnetic disk device 1 according to the first embodiment. 1, the magnetic disk device 1 includes a head disk assembly (HDA) (to be described later), a driver IC 20, a head amplifier integrated circuit (hereinafter, may be referred to as a head amplifier IC or a preamplifier) ​​30, a volatile memory 70, a non-volatile memory 80, a buffer memory 90, and a system controller 130 which is a one-chip integrated circuit. The magnetic disk device 1 is also connected to a host system (host) 100.

[0009] The HDA has a magnetic disk (hereinafter referred to as "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 attached to the spindle motor 12 and rotates when driven by the spindle motor 12. The arm 13 and the voice coil motor 14 constitute an actuator. Driven by the voice coil motor 14, the actuator controls the movement of the magnetic head 15 mounted on the arm 13 to a predetermined position on the disk 10. Two or more disks 10 and magnetic heads 15 may be provided.

[0010] 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 write 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. Write data may be simply referred to as data, read data may be simply referred to as data, and write data and read data may be collectively referred to as data.

[0011] The disk 10 is allocated with the following areas to which data can be written: a user data area 10a available to the user, a media cache area 10b for temporarily holding data (or commands) transferred from the host 100 or the like before writing them to a specified area in the user data area 10a, and a system area 10c for recording information required for system management. Hereinafter, the direction perpendicular to the radial direction of the disk 10 is referred to as the circumferential direction. Note that the media cache area 10b does not necessarily have to be allocated, and the system area 10c may be allocated to the non-volatile memory 80 or the like.

[0012] The magnetic head (hereinafter also referred to as head) 15 has a slider as its main body, and includes a write head 15W and a read head 15R mounted on the slider. The write head 15W writes data to a track on the disk 10. The read head 15R reads data recorded on the track on the disk 10. The write head 15W may be simply referred to as the head 15, the read head 15R may be simply referred to as the head 15, or the write head 15W and the read head 15R may be collectively referred to as the head 15. The term "track" is used to mean one of a number of regions obtained by dividing the disk 10 in the radial direction, one of a number of regions obtained by dividing the disk 10 in the circumferential direction, data written at a specific position on the disk 10, data written in a sector, and various other meanings. The radial width of the track is referred to as the track width, and the central position of the track width is referred to as the track center.

[0013] The driver IC 20 controls the driving of the spindle motor 12 and the VCM 14 under the control of a system controller 130 (more specifically, an MPU 60, which will be described later). The head amplifier IC (preamplifier) ​​30 includes a read amplifier and a write driver. The read amplifier amplifies a read signal read from the disk 10 by the read head 15R and outputs it to the system controller 130 (more specifically, a 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.

[0014] The volatile memory 70 is a semiconductor memory in which stored data is lost when the power supply is cut off. The volatile memory 70 stores data and the like required for processing in each part of the magnetic disk device 1. The volatile memory 70 is, for example, a dynamic random access memory (DRAM) or a synchronous dynamic random access memory (SDRAM). The non-volatile memory 80 is a semiconductor memory that records stored data even when the power supply is cut off. The non-volatile memory 80 is, for example, a NOR type or NAND type flash ROM (Flash Read Only Memory: FROM).

[0015] The buffer memory 90 is a semiconductor memory that temporarily records data and the like transmitted and received between the magnetic disk device 1 and the host 100. The buffer memory 90 may be integrated with the volatile memory 70. The buffer memory 90 may be, for example, a DRAM, a SRAM (Static Random Access Memory), a SDRAM, or a FeRAM (Ferroelectric Random Access Memory). Examples include MRAM (Magnetoresistive Random Access Memory) and MRAM (Magnetoresistive Random Access Memory).

[0016] The system controller (controller) 130 is realized, for example, by using a large scale integrated circuit (LSI) called a System-on-a-Chip (SoC) in which multiple elements are integrated on 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 a driver IC 20, a head amplifier IC 30, a volatile memory 70, a non-volatile memory 80, a buffer memory 90, and a host system 100.

[0017] The R / W channel 40 executes signal processing of read data transferred from the disk 10 to the host 100 and write data transferred from the host system 100 in response to instructions from the MPU 60, which will be 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, a head amplifier IC, the HDC 50, the MPU 60, etc. The HDC 50 controls data transfer between the host system 100 and the R / W channel 40 in response to instructions from the MPU 60, which will be described later. The HDC 50 is electrically connected to, for example, the R / W channel 40, the MPU 60, the volatile memory 70, the non-volatile memory 80, and the buffer memory 90.

[0018] 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 executes servo control for positioning the head 15. The MPU 60 also controls the spindle motor (SPM) 12 via the driver IC 20 to rotate the disk 10. The MPU 60 controls the operation of writing data to the disk 10 and selects a destination for storing the write data. The MPU 60 also controls the operation of reading data from the disk 10 and controls processing of the read data. The MPU 60 is connected to each part of the magnetic disk device 1. The MPU 60 is electrically connected to, for example, the driver IC 20, the R / W channel 40, the HDC 50, and the like.

[0019] The MPU 60 includes a write control unit 610 that controls write processing, and a read control unit 620 that controls read processing. The MPU 60 executes the processing of each of these units, such as the write control unit 610 and the read control unit 620, on firmware. The MPU 60 may include each of these units, such as the write control unit 610 and the read control unit 620, as a circuit.

[0020] The write control unit 610 controls the data write process according to a command from the host 100 or the like. The write control unit 610 controls the VCM 14 via the driver IC 20, positions the head 15 at a predetermined position on the disk 10, and writes 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 simply referred to 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". Also, "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 simply referred to as "positioning" or "positioning".

[0021] The write control unit 610 positions the head 15 (write head 15W) at a target position during write processing (hereinafter, may be referred to as a positioning target position, a target position, or a target write position) and writes data. The write control unit 610 positions the head 15 at the target write position and performs random writing. In other words, the write control unit 610 positions the head 15 at a target radial position during write processing (hereinafter, may be referred to as a target radial position or a target write radial position) at a specified circumferential position and randomly writes data. For example, the write control unit 610 controls the head 15 to be positioned at the target write radial position at a specified circumferential position and randomly writes a specified sector.

[0022] The write control unit 610 controls the head 15 to be positioned at the target write position, and can randomly write data to a predetermined position (hereinafter, sometimes referred to as the actual position or actual write position). The actual write position may be the target write position, or may be a position shifted from the target write position. Hereinafter, "the center of the write head 15W being radially displaced from a predetermined target write position" may be expressed as "the write head 15W going off-track from a predetermined track." The write control unit 610 also has a write processing circuit C1, which will be described later in the description of Fig. 4. The write processing circuit C1 may be provided outside the write control unit 610.

[0023] The read control unit 620 controls the data read process according to commands from the host 100 etc. The read control unit 620 controls the VCM 14 via the driver IC 20, and places the head 15 at a predetermined position on the disk 10 to read the data. The read control unit 620 may read the data randomly or sequentially.

[0024] The read control unit 620 places the head 15 (read head 15R) at the target read position and reads the data. The read control unit 620 places the head 15 at the target read position and reads. In other words, the read control unit 620 controls the head 15 to be placed at the target read radial position at a predetermined circumferential position and reads the data. For example, the read control unit 620 controls the head 15 to be placed at the target read radial position at a predetermined circumferential position and reads a predetermined sector. The read control unit 620 may control the head 15 along the target read path to read a predetermined track.

[0025] Here, the basic concept of the embodiment will be described. The head (magnetic recording / reproducing head) 15 of the magnetic disk device 1 has its radial position controlled by an actuator including a VCM 14 etc. so that the head stays on a track formed in the circumferential direction of the magnetic disk 10. Hereinafter, the above control is also referred to as positioning control. When an external vibration or shock is applied to the magnetic disk device 1 equipped with the actuator including the head and the magnetic disk 10, the head 15 may write at an actual position that is different from the target position. To prevent the above-mentioned deviation from occurring, the magnetic disk device 1 controls the positioning of the head 15 by a feedback loop. Hereinafter, the "deviation between the target position and the actual position" is also referred to as a "positioning error."

[0026] If the positioning error due to the positioning control is large, there is a high risk of erasing data recorded on adjacent tracks, so a threshold value (WOS: Write Offtrack Slice) is set for the positioning error, and if this threshold value is exceeded, the write operation is stopped to prevent erasure of data recorded on adjacent tracks. Hereinafter, the threshold value is also referred to as the "write offtrack slice," "write offtrack threshold," or "offtrack slice."

[0027] The write process will now be described with reference to the drawings. Fig. 2 is a diagram showing an example of a write process of the magnetic disk device 1 according to the first embodiment. Fig. 2 shows three consecutive tracks arranged in the order of track Trk0, track Trk1, and track Trk2 from the outer periphery along the radial direction of the disk 10. In the upper, middle, and lower stages shown in Fig. 2, data is written in the order of track Trk1, track Trk2, and track Trk0, respectively.

[0028] As shown in the upper part of FIG. 2, each data area of ​​the data written on the track Trk0 and the track Trk2 has an erase width EW. The data area D2 of the data written on the track Trk2 is written with a deviation (offset) toward the track Trk1. More specifically, the data area D2 is positioned with an offset by an error (positioning error, offset amount, or off-track amount) PE2 toward the outer periphery. The data area D0 of the data written on the track Trk0 is written with a deviation toward the track Trk1. More specifically, the data area D0 is positioned with an offset by an error PE0 toward the inner periphery.

[0029] As described above, the data sectors on tracks Trk0 and Trk2 are written with offset errors PE0 and PE2, so the track width of data area D1 for the data written to track Trk1 is TW1, which is the track width from the inner edge of data area D0 to the outer edge of data area D2. If the inner direction is taken as positive, track width TW1 is expressed by the following formula (1). TW1 is the track width, TP is the track pitch, EW is the erase width, PE0 is the error of data area D0, and PE2 is the error of data area D2. TW1 = 2TP-EW-(PE0-PE2) (1)

[0030] Next, as shown in the middle part of FIG. 2, a case will be described where the errors PE0, PE2 of the data areas D0, D2 are the upper limit value PEMX. The upper limit value PEMX is the upper limit of the absolute value of the errors PE0 and PE2. If the track width TW1 at this time is the lower limit value TWL at which user data can be read normally, the lower limit value TWL is expressed by the following formula. Note that TWL represents the lower limit value and PEMX represents the upper limit value. TWL=2TP-EW-2PEMX

[0031] From the above formula, it is defined that the TPI margin value TM is twice the upper limit value PEMX. The TPI margin value TM is the amount of track squeeze that allows the read error rate. The TPI margin value TM is expressed by the following formula (2). TM represents the TPI margin value. TM=2PEMX=2TP-EW-TWL···(2)

[0032] From the above formulas (1) and (2), the track width TW1 is expressed by the following formula (3). TW1 = TWL + TM - (PE0 - PE2) (3) From equation (3), it can be seen that 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 if the value obtained by subtracting the positioning error PE2 from the positioning error PE0 is equal to or less than the TPI margin value TM, the track width TW1 is equal to or more than the lower limit value TWL. In other words, when the difference between the positioning errors PE0 and PE2 is equal to or less than the TPI margin value TM, the user data written to the track Trk1 is preserved.

[0033] Next, as shown in the lower part of FIG. 2, a case will be described in which the target position when writing to the track Trk0 is offset by a correction amount OFS0 when the positioning error PE2 is known. The relationship between the positioning error PE0, the correction amount OFS0, and the upper limit value PEMX can be expressed by the following formula: Here, OFS0 represents the correction amount. PE0≦OFS0+PEMX

[0034] From the above formula, formula (2), and formula (3), the track width TW1 is expressed by the following formula. TW1 ≧ TWL + PEMX + (PE2 - OFS0) Therefore, when the correction amount OFS0 is the positioning error PE2, the track width TW1 is expressed by the following equation (4). TW1 ≥ TWL + PEMX (4) Equation (4) shows that when the correction amount OFS0 is the positioning error PE2, the track width TW1 becomes wider than the lower limit TWL, which is the read limit, by the maximum positioning error (upper limit) PEMX. However, this method does not take into consideration the protection of data written to track Trkm1 (see FIG. 3), which is adjacent to the outer periphery of track Trk0.

[0035] The process for protecting the adjacent tracks Trk1 and Trkm1 will be described below. Fig. 3 is a diagram showing an example of a write process of the magnetic disk device 1 according to the first embodiment. In addition to the three tracks Trk0, Trk1, and Trk2 shown in the upper part, two tracks Trkm2 and Trkm1 are shown in the lower part of Fig. 3, and data is written in the order of tracks Trk1, Trk2, Trkm1, and Trkm2.

[0036] 3, the data area D2 of the track Trk2 is written with an offset of an error PE2 toward the outer periphery, and the data area Dm2 of the track Trkm2 is written with an offset of an error PEm2 toward the inner periphery. Data is written to the track Trk0 with the target position offset by a correction amount OFS0. Here, the possible range of error PE0 when writing data to track Trk0 is expressed by the following formula (5). OFS0-PEMX≦PE0≦OFS0+PEMX (5)

[0037] In this case, the lower limit of the track width TW1 of the data region D1 and the lower limit of the track width TWm1 of the data region Dm1 are respectively expressed by the following formulas (6a) and (6b): TWm1 is the track width of the data region Dm1. TW1≧TWL+PEMX-(OFS0-PE2)···(6a) TWm1≧TWL+PEMX+(OFS0-PEm2) (6b) The correction amount of the target position that balances 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). OFS0 = (PE2 + PEm2) / 2 (7) That is, the correction amount OFS is half the value obtained by adding the positioning error PE of the sector two tracks inward from the target sector to the positioning error PEm2 of the sector two tracks outward from the target sector. Hereinafter, the "positioning error" may be referred to as the "error position," and the "correction amount" may be referred to as the "target position."

[0038] From the above, by considering the positioning error (in one example, error PE2) of the data written on the track located two tracks inward (in one example, track Trk2) and the positioning error (in one example, error PEm2) of the data written on the track located two tracks outward (in one example, track Trkm2), it becomes possible to protect existing data on the tracks (in one example, tracks Trk1 and Trkm1) adjacent to the track to be written (in one example, track Trk0) under the same conditions. This makes it possible to prevent the width of any of the tracks from narrowing, thereby reducing the integrity of the user data.

[0039] Next, a control configuration for calculating the target position will be described. Fig. 4 is a block diagram showing an example of the control configuration of the magnetic disk device 1 according to the first embodiment, and represents the write processing circuit C1 of the write control unit 610 in Fig. 1. In Fig. 4, the address of the target sector (C, S) omits the head number and indicates only the cylinder number C and the sector number S. The cylinder number C is a number consecutively assigned to the tracks 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 may also be referred to as a track number. As shown in FIG. 4, the write processing circuit C1 of the write control unit 610 has an offtrack write table 611, a target position trajectory generating circuit 612, a physical target position transducer 614, a controller 615, and an actuator 616.

[0040] The target sector (C, S) is converted by a physical target position converter 614 into a physical target position R(C, S), which is a radial position of the disk 10. The physical target position R(C, S) is added with a target position correction amount OFS(C, S) to become a corrected target position R1(C, S). The difference between the physical position Y of the magnetic head 15 and the corrected target position R1 becomes a positioning error PE(C, S) in the sector (C, S). The positioning error PE is negatively fed back to the controller 615 and output as a control amount U to an actuator 616. The actuator 616 receives the control amount U as an input and outputs the physical position Y of the magnetic head 15, which is a radial position of the disk 10.

[0041] Further, the off-track write table 611 is referenced from the address of the target sector (C, S), and a positioning error PE(C+2, S) of the data area of ​​the data written in the sector (C+2, S) located two tracks inward and a positioning error PE(C-2, S) of the data area of ​​the data written in the sector (C-2, S) located two tracks outward are output. The positioning errors PE(C+2, S) and PE(C-2, S) are input to the target position trajectory generating circuit 612, which outputs a correction amount OFS(C, S) of the target position according to the input. As the correction amount OFS(C, S), for example, the following formula (8) can be obtained according to formula (7). OFS(C,S)=(PE(C+2,S)+PE(C-2,S)) / 2···(8)

[0042] Next, a mechanism for registering a positioning error in the off-track write table 611 will be described. 5 is a diagram showing an example of a control configuration of the magnetic disk device 1 according to the first embodiment. FIG 5 shows a configuration for registering and updating a positioning error in the off-track write table 611. As shown in FIG. 5, the positioning error PE(C,S) during writing to the target sector (C,S) is input to an absolute value circuit 617, which outputs the absolute value PEA of the positioning error PE(C,S). The absolute value PEA is compared with a predetermined registration judgment threshold Th in the operational amplifier OP1. If the absolute value PEA exceeds the registration judgment threshold Th, the operational amplifier OP1 outputs a registration flag RF1 as 1, and if the absolute value PEA does not exceed the registration judgment threshold Th, the operational amplifier OP1 outputs the registration flag RF1 as 0.

[0043] On the other hand, the off-track write table reference update block (hereinafter also referred to as the 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 means the same direction as the positioning error PE(C, S). 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 if the absolute value PEA exceeds the maximum positioning error PEP, it outputs the update flag RF2 as 1, and if the absolute value PEA does not exceed the maximum positioning error PEP, it outputs the update flag RF2 as 0. If 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 that the operational amplifier OP2 outputs the update flag RF2 as 1.

[0044] If the positioning error PE(C,S) is less than 0, the operational amplifier OP3 outputs the flag DPE as 1, and if the positioning error PE(C,S) is not less than 0, the operational amplifier OP3 outputs the flag DPE as 0. In other words, the sign of the positioning error PE(C,S) can be identified by the flag DPE. 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 off-track write table 611 updates or newly registers information according to the sign of the positioning error PE(C, S).

[0045] Next, the target position correction amount OFS calculated by the target position trajectory generating circuit 612 will be specifically described. 6 is a schematic diagram showing the correction amount OFS of the target position and the positioning error PE of the data written in the sector two tracks ahead. FIG. 6 is a diagram for explaining the operation of the target position trajectory generating circuit 612. As shown in FIG. 6, data of positioning error PE(C-2,Si) is written to sector (C-2,Si) located two tracks outward from target sector (C,Si) (i=1,2,...,6), and data of positioning error PE(C+2,Si) is written to sector (C+2,Si) located two tracks inward from target sector (C,S).

[0046] The positioning errors PE(C-2, Si) and PE(C+2, Si) can be referenced from the off-track write table 611, and are indicated by black circles in the example shown in FIG. The correction amount OFS(C,Si) of the target position of the target sector (C,Si) is a 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. In the example shown in FIG. 6, 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.

[0047] As described above, the correction amount OFS(C,Si) of the target position is generated, so that the user data on the sectors (C-1,Si) and (C+1,Si) (not shown) on the tracks indicated by cylinder numbers C-1 and C+1 adjacent to the track indicated by cylinder number C are preserved. In the example shown in Fig. 6, the correction amount OFS(C,Si) is the midpoint between the positioning errors PE(C-2,Si) and PE(C+2,Si), but is not limited to the midpoint. For example, when priority is given to making the target position trajectory along the track center, the positioning target position may be corrected to between the correction amount OFS(C,Si) shown in Fig. 6 and the track center.

[0048] However, in a magnetic disk device 1 that performs random access, there are variations in the write state two tracks ahead of the target track. Therefore, generating a target position using the midpoint between the positioning error of data written in a sector two tracks inside and the positioning error of data written in a sector two tracks outside may not be optimal for the purpose of protecting data in a sector adjacent to the target sector.

[0049] A case will now be described in which the midpoint of the positioning error of data written two tracks ahead is not used as the correction amount OFS of the target position. FIG. 7 is a schematic diagram showing the correction amount OFS of the target position and the positioning error PE of the data written in the sector two tracks ahead. As shown in Figure 7, some sectors (C-2, S4) and (C-2, S5) two tracks outward from the target sector (C, Si) and some sectors (C+2, S1), (C+2, S2), (C+2, S5), and (C+2, S6) two tracks inward from the target sector (C, Si) are in a recorded (registered) state (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 as black circles on the thick line TL.

[0050] In the example shown in Fig. 7, sectors (C-2, S1), (C-2, S2), (C-2, S3), (C-2, S6), (C+2, S3), and (C+2, S4) are either unrecorded (unregistered) or have data written thereto at a time earlier (before) than sectors (C-1, Si) and (C+1, Si) one track ahead (not shown). Therefore, since the above sectors do not affect sectors (C-1, Si) or sectors (C+1, Si), they are determined to be inactive and the positioning error is considered to be zero.

[0051] Here, when focusing on sectors (C, S1), (C, S2), and (C, S6), sectors (C-2, S1), (C-2, S2), and (C-2, S6) on the outer periphery of two tracks are inactive, and sectors (C+2, S1), (C+2, S2), and (C+2, S6) on the inner periphery of two tracks are active. In other words, sectors (C+1, S1), (C+1, S2), and (C+1, S6) not shown in the figure are subject to interference from sectors (C+2, S1), (C+2, S2), and (C+2, S6), but sectors (C-1, S1), (C-1, S2), and (C-1, S6) not shown in the figure are not subject to interference from sectors (C-2, S1), (C-2, S2), and (C-2, S6).

[0052] At this time, by setting the target position correction amount OFS(C,S1),(C,S2),(C,S6) to a position closer to the outer periphery than the midpoint between 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 integrity of the data written to sectors (C+1,S1),(C+1,S2),(C+1,S6) on the track adjacent to the inner periphery can be improved. For example, in the case of Figure 7, 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 or equal to 1. In other words, line segment L1b is greater than or equal to line segment L1a, line segment L2b is greater than or equal to line segment L2a, and line segment L6b is greater than or equal to line segment L6a.

[0053] Next, looking at sector (C, S4), the sector (C-2, S4) two tracks outside is active, and the sector (C+2, S4) two tracks inside is inactive. That is, sector (C-1, S4) (not shown) is subject to interference from sector (C-2, S4), but sector (C+1, S4) (not shown) is not subject to interference from sector (C+2, S4). At this time, by setting the target position correction amount OFS(C, S4) to a position closer to the inner side than the midpoint between the positioning errors PE(C-2, S4) and PE(C+2, S4), it is possible to improve the integrity of the data in the sector (C-1, S4) on the track adjacent to the outer side. For example, in FIG. 7, the ratio of the length of line segment L4a to the length of line segment L4b is 1 or more. In summary, by correcting the positioning target position of the target sector so as to offset it toward the sector determined to be inactive, the integrity of data in sectors adjacent to the target sector can be improved.

[0054] Furthermore, in a magnetic disk device 1 that performs random access, there are cases where the write positioning error becomes discontinuous on the same track. An example in which the positioning error becomes discontinuous will be described below. FIG. 8 is a schematic diagram showing the correction amount OFS of the target position and the positioning error PE of the data written in the sector two tracks ahead. As shown in FIG. 8, in sector (C-2, S+i) (i = ···, -2, -1, 0, 1, 2, ···), a discontinuous positioning error occurs between sector (C-2, S) and sector (C-2, S+1), and in sector (C+2, S+i), a discontinuous positioning error occurs between sector (C+2, S) and sector (C+2, S+1).

[0055] In such a case, discontinuity occurs between the correction amount OFS(C,S) and the correction amount OFS(C,S+1) between the target sector (C,S) and the target sector (C,S+1). Because the magnetic head 15 has mass and there is an upper limit to the current that can be applied to move the magnetic head 15, the head positioning control system cannot accurately track the target position trajectory shown in Fig. 8, and there is a risk of destroying user data in sectors (C-1,S+1) and (C+1,S+1) (not shown) on the track adjacent to the target sector (C,S+1) in the radial direction.

[0056] A modification of the first embodiment that can solve the above-mentioned problems will be described with reference to FIG. (Modification) FIG. 9 is a schematic diagram showing the correction amount OFS of the target position and the positioning error PE of the data written in the sector two tracks ahead. In the explanation of the modified example, the correction amount OFS(C, S) of the target position in equation (8) is referred to as the "target position correction amount initial value" or the "correction amount initial value." 9, first, the auxiliary offset amount OFST(C,S) is calculated, which is the midpoint between the correction amount initial value OFS(C,S-1) of the sector (C,S-1) adjacent in the circumferential direction to the target sector (C,S) and the correction amount initial value OFS(C,S+1) of the sector (C,S+1). The auxiliary offset amount OFST(C,S) is expressed by the following formula (9). OFST(C,S)=(OFS(C,S-1)+OFS(C,S+1)) / 2···(9) In other words, the supplementary offset amount OFST(C,S) is half the value obtained by adding the initial correction amount value OFS(C,S+1) to the initial correction amount value OFS(C,S−1).

[0057] Next, the optimum correction amount OFSR(C,S) of the target position, which is the midpoint between the initial correction amount OFS(C,S) of the sector (C,S) and the auxiliary offset amount OFST(C,S), is calculated. The optimum correction amount OFSR(C,S) is expressed by the following formula (10). OFSR(C,S)=(OFS(C,S)+OFST(C,S)) / 2···(10) In one example, the optimum correction amount value OFSR(C,S) is half the value obtained by adding the auxiliary offset amount OFST(C,S) to the initial correction amount value OFS(C,S). The magnetic disk device 1 according to the modified example can correct the initial correction amount value OFS(C, S) to the optimal correction amount value OFSR(C, S) that corresponds to the discontinuity by the above-mentioned procedure.

[0058] In summary, the magnetic disk device 1 calculates initial correction amount values ​​OFS(C,S-1), OFS(C,S+1) for a pair of sectors (C,S-1), (C,S+1) adjacent to the target sector (C,S) in the circumferential direction, calculates an auxiliary offset amount OFST(C,S) which is the midpoint of the initial correction amount values ​​OFS(C,S-1), OFS(C,S+1) for the pair of sectors (C,S-1), (C,S+1), and calculates an optimal correction amount value OFSR(C,S) which is the midpoint between the initial correction amount value OFS(C,S) and the auxiliary offset amount OFST(C,S). The correction amount OFSR is not limited to being the midpoint between the correction amount initial value OFS(C, S) and the supplemental offset amount OFST(C, S), and may be, for example, between the midpoint and the correction amount initial value OFS(C, S). Similarly, the initial correction amount value OFS(C, S+1) can be corrected to the optimum correction amount value OFSR(C, S+1).

[0059] By correcting the initial correction amount OFS(C, S) to the optimal correction amount OFSR(C, S) as described above, it is possible to generate an optimal correction amount for the target position that alleviates the discontinuity in the correction amount for the target position caused by discontinuity in the positioning error of the data written in the sector two tracks away. When equation (10) is substituted into equation (9), the optimum correction amount OFSR(C, S) is expressed by the following equation (11). OFSR(C,S)=OFS(C,S) / 2+OFS(C,S-1) / 4+OFS(C,S+1) / 4...(11)

[0060] From formula (11), it can be seen that the optimum correction amount OFSR(C,S) is the weighted moving average of the initial correction amount values ​​OFS(C,S-1), OFS(C,S), and OFS(C,S+1) of the three consecutive sectors (C,S-1), (C,S), and (C,S+1). Generalizing this, the optimum correction amount value OFSR(C,S) is expressed by the following formula (12).

number

[0061] Alternatively, the initial correction amount values ​​OFS may be calculated for a plurality of sectors, and the optimal correction amount value OFSR may be calculated by linearly combining the initial correction amount values ​​OFS using equation (12). More specifically, an initial correction amount value OFS for a sector that is a predetermined number before the target sector (one side in the circumferential direction) and an initial correction amount value OFS for a sector that is a predetermined number after the target sector (the other side in the circumferential direction) are calculated, and the multiple initial correction amount values ​​OFS are linearly combined using equation (12). Using the example of FIG. 9, the initial correction values ​​OFS(C,S-2), (C,S-1), (C,S), (C,S+1), and (C,S+2) may be calculated for sectors (C,S-2), (C,S-1), (C,S), (C,S+1), and (C,S+2), respectively, and the optimal correction value OFSR(C,S) may be calculated using equation (12).

[0062] The effects of the first embodiment will be described. According to the magnetic disk device 1 of the first embodiment, when writing data to a first sector (in one example, sector (C, S)), the magnetic disk device 1 corrects the positioning target position of the first sector based on the positioning error of a second sector (in one example, sectors (C-2, S), (C+2, S)) located two tracks away from the first sector in the radial direction. Therefore, a dynamic positioning target position can be generated based on the positioning error of the second sector, data on tracks adjacent to the first sector can be protected, and the excess rate of off-track slices can be leveled. This makes it possible to obtain the magnetic disk device 1 and the control method for the magnetic disk device 1 that can prevent the quality deterioration of adjacent tracks without degrading the write performance due to an increase in the frequency of write operation stop due to detection of an excess of off-track slices as described later.

[0063] Incidentally, the magnetic disk device 1 normally has a write-off track processing circuit, which stops the write operation if it determines that the absolute value of the positioning error PE exceeds the write-off track slice absolute value WOS before writing data to the target sector. However, since the positioning error PE is detected by the sampling process, it may be written beyond the off-track slice WOS. The sampling process will be described below with reference to FIG.

[0064] Fig. 10 is a schematic diagram for explaining an example of the sampling process. In Fig. 10, in addition to the trajectory of the positioning error PE of the magnetic head 15 shown by a solid curve and a dashed curve, the open / closed state of the write gate WG is also shown. Moreover, PE1, PE2,..., PE7 shown by white circles indicate the positioning errors PE intermittently detected by the sampling process. 10, in the magnetic disk device 1, a sampling process is performed to detect positioning error PE at a predetermined time interval T. In the example shown in Fig. 10, positioning errors PE1, PE2, PE3, and PE4 are located within the off-track slice ±WOS, and positioning error PE5 is located outside the off-track slice ±WOS.

[0065] After detecting the positioning error PE5, the magnetic disk device 1 (write control unit 610) closes the write gate WG, so that data with the positioning error PE5 that exceeds the off-track slice ±WOS is written to the sector. In summary, when detecting the positioning error PE by sampling, a delay occurs between when the physical position of the magnetic head 15 exceeds the off-track slice ±WOS and when it is detected, and the write operation continues. The amount of overrun from the off-track slice ±WOS at this time is called the overrun amount OVR.

[0066] If the absolute value of the maximum value of the overrun amount OVR is the overrun maximum absolute value OVMX, the upper limit value PEMX of the absolute value of the positioning error is the sum of the off-track slice absolute value WOS and the overrun maximum absolute value OVMX, and is expressed by equation (13). Note that PEMX is the maximum absolute value of the positioning error, WOS is the off-track slice absolute value, and OVMX is the overrun maximum absolute value. PEMX = WOS + OVMX (13) Moreover, from equation (2), the TPI margin value TM is expressed by the following equation (14). TM = 2(WOS + OVMX) (14)

[0067] Hereinafter, a magnetic disk device 1 according to a second embodiment in which the correction amount OFS of the target position is determined by taking into account the off-track slice absolute value WOS will be described. In the second embodiment described below, the same parts as those in the first embodiment described above are given the same reference numerals, and detailed descriptions thereof will be omitted or simplified, and the description will focus on parts that are different from the first embodiment. Second embodiment Fig. 11 is a diagram showing an example of a write process of the magnetic disk device 1 according to the second embodiment. The upper part of Fig. 11 is a schematic diagram expressing the middle part of Fig. 2 using the off-track slice absolute value WOS and the overrun maximum value absolute value OVMX. 11, tracks Trk0, Trk1, and Trk2 are set with predetermined (predetermined) off-track slices ±WOS. The off-track slice on the outer periphery side is −WOS, and the off-track slice on the inner periphery side is +WOS.

[0068] The positioning error of the data area D2 of the data written in the track Trk2 is the maximum value in the outer circumferential direction and is expressed by the following formula. -PEMX=-WOS-OVMX The positioning error of the data area D0 of the data written in the track Trk0 is the maximum value in the inner circumferential direction and is expressed by the following formula. +PEMX=+WOS+OVMX 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). 2TP=EW+TWL+2(WOS+OVMX)...(15)

[0069] The middle part of FIG. 11 shows a case where the positioning error PE2 of the track Trk2 is known and does not exceed the off-track slice -WOS on the outer circumferential side. At this time, when data is written to track Trk0 and the positioning error PE0 in data area D0 is a value that exceeds the off-track slice+WOS toward the inner periphery by the overrun maximum value OVMX, the positioning error PE0 is expressed by the following formula. PE0=+WOS+OVMX=+PEMX

[0070] At this time, the track width TW1 of the track Trk1 is expressed by the following formula from formulas (3) and (14). TW1=TWL+(WOS+OVMX)+PE2 Here, the positioning error PE2 satisfies the following condition. PE2>-WOS Therefore, the track width TW1 is expressed by the following formula. TW1>TWL+OVMX From the above formula, it is guaranteed that the track width TW1 has a margin with respect to the lower limit value TWL of the track width equal to or greater than the overrun maximum absolute value OVMX.

[0071] The lower part of FIG. 11 shows a case where the positioning error PE2 of the track Trk2 is known and exceeds the off-track slice -WOS on the outer circumferential side. At this time, the overrun amount OVR2 of the data area D2 is expressed by the following formula. OVR2=PE2+WOS Here, a new inner off-track slice WOS0p is generated by offsetting the inner off-track slice of the track Trk0 by OVR2 from +WOS. The off-track slice WOS0p is expressed by the following formula. WOS0p = 2WOS + PE2 (16)

[0072] 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 slice WOS0p toward the inner circumference by the overrun maximum absolute value OVMX, the positioning error PE0 is expressed by the following formula. PE0=WOS0p+OVMX Considering the above equation, equation (3), and equation (14), the track width TW1 is expressed by the following equation (17). TW1 = TWL + OVMX (17)

[0073] From equation (17), it is guaranteed that the track width TW1 has a margin of the overrun maximum absolute value OVMX with respect to the lower limit value TWL of the track width. From the above, when the positioning error PE2 of track Trk2, which is two tracks inward from track Trk0, is known, by setting the off-track slice WOS0p on the inner side of track Trk0 based on the positioning error PE2, it is possible to ensure that the track width of track Trk1, which is adjacent to the inner side, has a margin of at least the overrun maximum absolute value OVMX relative to the lower limit value TWL.

[0074] However, the absolute value of the new inner diameter off-track slice WOS0p of the track Trk0 is equal to or less than the absolute value of the original inner diameter off-track slice+WOS, and satisfies the following formula. |WOS0p|≦|+WOS| In other words, since the new inner off-track slice WOS0p is formed by narrowing the original inner off-track slice+WOS, the rate of occurrence of off-track on the inner side increases, which may degrade write performance.

[0075] Therefore, the target position for positioning of track Trk0 is offset by a correction amount OFS0 to balance the probability of exceeding the outer off-track slice -WOS of track Trk0 to the outer side and the probability of exceeding the new inner off-track slice WOS0p to the inner side. In other words, the target position should be offset by the correction amount OFS0 that satisfies the following formula. OFS0-(-WOS)=WOS0p-OFS0 That is, the correction amount OFS0 is expressed by the following equation (18). OFS0 = (WOS0p - WOS) / 2 (18)

[0076] Furthermore, a case will be considered in which an off-track slice -WOS on the outer periphery of track Trk0 changes due to a positioning error in the inner periphery direction of track Trkm2, which is two tracks outer than track Trk0. Hereinafter, with reference to FIG. 12, a correction amount OFS0 when the off-track slice −WOS on the outer periphery side and the off-track slice +WOS on the inner periphery side of the track Trk0 change will be described.

[0077] As shown in FIG. 12, the positioning error PEm2 of the track Trkm2 is known, and the positioning error PEm2 exceeds the off-track slice+WOS on the inner periphery side. At this time, the overrun amount OVRm2 is expressed by the following formula. OVRm2=PEm2-WOS Here, a new outer circumferential off-track slice WOS0m is generated by offsetting the outer circumferential off-track slice of track Trk0 by OVRm2 from -WOS. WOS0m = -WOS + OVRm2 That is, the off-track slice WOS0m is expressed by the following equation (19). WOS0m = -2WOS + PEm2 (19)

[0078] At this time, a balance is maintained between the probability of exceeding the off-track slice WOS0p on the inner side of the track Trk0 to the inner side and the probability of exceeding the off-track slice WOS0m on the outer side to the outer side. In other words, the target position is offset by the correction amount OFS0 that satisfies the following formula. OFS0-WOS0m=WOS0p-OFS0 That is, the correction amount OFS0 is expressed by the following equation (20). OFS0=(WOS0p+WOS0m) / 2···(20)

[0079] Next, a control configuration for calculating the target position will be described. FIG. 13 is a block diagram showing an example of a control configuration of the magnetic disk device 1 according to the second embodiment, and represents the write processing circuit C1 of the write control unit 610 in FIG. As shown in Fig. 13, the write processing circuit C1 of the write control unit 610 has a compression processing circuit 613, operational amplifiers OP4 and OP5, and an OR gate G2. The compression processing circuit 613 receives information on the positioning error PE(C+2,S) of data written two tracks inward from the target sector (C,S), information on the positioning error PE(C-2,S) of data written two tracks outward, a default TPI margin value TM, and a default write off-track slice absolute value WOS that does not depend on the sector. The compression processing circuit 613 outputs off-track slices WOSp and WOSm according to these inputs to the operational amplifiers OP4 and OP5.

[0080] Here, the off-track slice WOSp on the inner circumference side is a default value +WOS if the positioning error PE(C+2,S) of the data in the sector (C+2,S) two tracks inward does not exceed the default write off-track slice -WOS on the outer circumference side, and if it does, the formula (16) is applied. That is, the off-track slice WOSp on the inner circumference side is expressed by the following formula. WOSp = +WOS (PE(C+2,S)≧-WOS) WOSp=2WOS+PE(C+2,S) (PE(C+2,S)<-WOS)

[0081] In addition, the outer off-track slice WOSm is a default value -WOS if the positioning error PE(C-2,S) of the data in the sector (C-2,S) two tracks outward does not exceed the default off-track slice +WOS on the inner side, and if it does, the formula (19) is applied. In other words, the outer off-track slice WOSm is expressed by the following formula. WOSm = -WOS (PE(C-2,S)≦+WOS) WOSm=-2WOS+PE(C-2,S) (PE(C-2,S)>+WOS)

[0082] The positioning error PE(C,S) of the target sector (C,S) is compared with the off-track slice WOSp on the inner circumference side by the operational amplifier OP4, and with the off-track slice WOSm on the outer circumference side by the operational amplifier OP5. If the positioning error PE(C,S) exceeds either the off-track slice WOSp or the off-track slice WOSm, the OR gate G2 outputs a write inhibit flag WINH. When the system controller 130 receives the write inhibit flag WINH, it stops the write operation. The above-described operation ensures that the track widths of the sectors (C+1, S) and (C-1, S) adjacent to the target sector (C, S) are equal to or greater than the lower limit TWL.

[0083] On the other hand, the contraction processing circuit 613 also outputs the off-track slices WOSp, WOSm to the target position trajectory generating circuit 612. The target position trajectory generating circuit 612 performs the calculation of equation (20) based on the input off-track slices WOSp, WOSm. The target position trajectory generating circuit 612 outputs a correction amount OFS(C,S) of the target position obtained by the calculation. 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 a differentiator.

[0084] Next, the target position correction amount OFS calculated by the target position trajectory generating circuit 612 will be specifically described. FIG. 14 is a schematic diagram showing the correction amount OFS of the target position, the positioning error PE of the data written in the sector two tracks ahead, and the off-track slices WOSp, WOSm for the target sector. As shown in FIG. 14, data of positioning error PE(C-2,Si) is written to sector (C-2,Si) located two tracks outward from target sector (C,Si) (i=1,2,...,8), and data of positioning error PE(C+2,Si) is written to sector (C+2,Si) located two tracks inward from target sector (C,S).

[0085] The positioning errors PE(C-2, Si) and PE(C+2, Si) can be referenced from the off-track write table 611, and are indicated by black circles in the example shown in FIG. The correction amount OFS(C,Si) of the target position of the target sector (C,Si) is indicated by a white circle in the example shown in FIG. In the example shown in FIG. 14, the off-track slice WOSp on the inner side and the off-track slice WOSm on the outer side with respect to the target sector (C, S) are indicated by dashed lines.

[0086] First, we will explain the correction amount OFS(C,Si) based on the off-track slices WOSm(C,Si) and WOSp(C,Si) when writing the target sectors (C,S1), (C,S2), (C,S4), (C,S5), (C,S7), and (C,S8). The data 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) when writing the sectors two tracks outside the target sector do not exceed the default inner off-track slice +WOS in the inner direction. Therefore, the outer off-track slices WOSm(C,S1), WOSm(C,S2), WOSm(C,S4), WOSm(C,S5), WOSm(C,S7), and WOSm(C,S8) when writing the target sectors (C,S1), (C,S2), (C,S4), (C,S5), (C,S7), and (C,S8) all become the default value -WOS.

[0087] Furthermore, when writing the sectors two tracks inward from the target sector, the data 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) do not exceed the default outer off-track slice -WOS in the outer direction. Therefore, the inner off-track slices WOSp(C,S1), WOSp(C,S2), WOSp(C,S4), WOSp(C,S5), WOSp(C,S7), and WOSp(C,S8) when writing the target sectors (C,S1), (C,S2), (C,S4), (C,S5), (C,S7), and (C,S8) all become the default value +WOS. From 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) are all zero.

[0088] Next, the correction amount OFS(C,Si) based on the off-track slices WOSm(C,Si) and WOSp(C,Si) when writing the target sector (C,S3) will be described. The positioning error PE(C-2, S3) when writing to sector (C-2, S3) two tracks outside the target sector (C, S3) exceeds the predetermined off-track slice + WOS in the inner direction. More specifically, the positioning error PE(C-2, S3) exceeds the off-track slice + WOS in the inner direction by the overrun amount OVR(C-2, S3).

[0089] The overrun amount OVR(C-2, S3) is expressed by the following formula. OVR(C-2,S3)=PE(C-2,S3)-WOS The outer off-track slice WOSm(C, S3) when writing to the target sector (C, S3) is a value offset from the default value -WOS by the excess overrun amount OVR(C-2, S3), and is expressed by the following formula. WOSm(C,S3)=-2WOS+PE(C-2,S3)

[0090] On the other hand, the positioning error PE(C+2,S3) when writing to sector (C+2,S3) two tracks inward from the target sector (C,S3) exceeds the predetermined off-track slice-WOS on the outer periphery side toward the outer periphery. More specifically, the positioning error PE(C+2,S3) exceeds the off-track slice-WOS by the overrun amount OVR(C+2,S3) toward the outer periphery.

[0091] The amount of overrun OVR(C+2,S3) is expressed by the following formula. OVR(C+2,S3)=PE(C+2,S3)+WOS The inner off-track slice WOSp(C, S3) is a value offset from the default value +WOS by the excess overrun amount OVR(C+2, S3), and is expressed by the following formula. WOSp(C, S3) = +2WOS + PE(C + 2, S3)

[0092] The correction amount OFS(C, S3) of the target position is the midpoint between the off-track slice WOSm(C, S3) on the outer periphery side and the off-track slice WOSp(C, S3) on the inner periphery side, and is therefore expressed by the following formula. OFS(C,S3)=(WOSp(C,S3)+WOSm(C,S3)) / 2 From the above 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). OFS(C,S3)=(PE(C+2,S3)+PE(C-2,S3)) / 2

[0093] Next, the correction amount OFS(C,Si) based on the off-track slices WOSm(C,Si) and WOSp(C,Si) when writing the target sector (C,S6) will be described. The positioning error PE(C-2, S6) when writing to sector (C-2, S6) two tracks outside the target sector (C, S6) exceeds the predetermined off-track slice + WOS on the inner side. More specifically, the positioning error PE(C-2, S6) exceeds the off-track slice + WOS by the overrun amount OVR(C-2, S6) in the inner direction.

[0094] The amount of overrun OVR(C-2, S6) is expressed by the following formula. OVR(C-2,S6)=PE(C-2,S6)-WOS The outer circumferential off-track slice WOSm(C, S6) is a value offset from the default value -WOS by the excess overrun amount OVR(C-2, S6), and is therefore expressed by the following formula. WOSm(C,S6)=-2WOS+PE(C-2,S6)

[0095] On the other hand, the positioning error PE(C+2,S6) when writing to sector (C+2,S6) two tracks inside the target sector (C,S6) does not exceed the default outer off-track slice -WOS. Therefore, the inner off-track slice WOSp(C,S6) becomes the default value +WOS. The correction amount OFS(C, S6) of the target position is the midpoint between the off-track slice WOSm(C, S6) on the outer periphery side and the off-track slice WOSp(C, S6) on the inner periphery side, and is therefore expressed by the following formula. OFS(C,S6)=(WOSm(C,S6)+WOS) / 2 From the above equation, the correction amount OFS(C, S6) can also be expressed by the following equation using the positioning error PE(C-2, S6). OFS(C,S6)=(-WOS+PE(C-2,S6)) / 2

[0096] The effects of the second embodiment will be described. According to the magnetic disk device 1 of the second embodiment, the magnetic disk device 1 corrects the positioning target position of the target sector according to the threshold value (off-track slices WOSp, WOSm) determined based on the positioning error of the sector two tracks ahead of the target sector. Therefore, it is possible to obtain dynamic movement of the target position as in the first embodiment, and to obtain the same effect as in the first embodiment.

[0097] In the second embodiment, the initial correction amount value OFS may be corrected to an optimum correction amount value OFSR that can deal with discontinuous positioning errors, similarly to the modified example of the first embodiment. The modified example of the second embodiment will be described below. (Modification) FIG. 15 is a schematic diagram showing the correction amount OFS of the target position and the off-track slices WOSp, WOSm for the target sector. As shown in FIG. 15, the off-track slice WOSp(C,S) on the inner side is discontinuous with the off-track slice WOSp(C,S+1) on the inner side, and the off-track slice WOSm(C,S) on the outer side is discontinuous with the off-track slice WOSm(C,S+1) on the outer side.

[0098] If a discontinuous positioning error occurs between sectors (C-2, S) and (C-2, S+1) not shown, and if a discontinuous positioning error occurs between sectors (C+2, S) and (C+2, S+1) not shown, then the discontinuous inner off-track slices WOSp(C, S), WOSp(C, S+1) and outer off-track slices WOSm(C, S), WOSm(C, S+1) described above will result. The trajectory of the target position correction initial values ​​OFS(C,S) and OFS(C,S+1) determined at the midpoint of the off-track slice described above has abrupt changes. The correction initial value OFS(C,S) is expressed by the following formula. OFS(C,S)=(WOSp(C,S)+WOSm(C,S)) / 2

[0099] 15, 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 in the circumferential direction to the target sector (C,S), and the correction amount optimum 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 optimum value OFSR(C,S) are expressed by the following formulas. OFST(C,S)=(OFS(C,S-1)+OFS(C,S+1)) / 2 OFSR(C,S)=(OFS(C,S)+OFST(C,S)) / 2

[0100] The optimum correction amount OFSR(C,S+1) of the target sector (C,S+1) can also be calculated in a similar manner. As described above, by correcting the initial correction amount OFS to the optimum correction amount OFSR, data written in radially adjacent sectors (in one example, sectors (C-1,Si), (C+1,Si)) can be protected even if the positioning error of data written two tracks ahead is discontinuous. Moreover, equations (11) and (12) can be applied in a similar manner.

[0101] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. Multiple embodiments can be combined as necessary. [Explanation of symbols]

[0102] 1...magnetic disk device, 10...magnetic disk, 15...magnetic head, 15W...write head, 130...system controller, 611...off-track write table, 612...target position trajectory generating circuit, 613...contraction processing circuit, PE...positioning error, Trkm2, Trkm1, Trk0, Trk1, Trk2...tracks, TW1, TWm1...track width, WOS0m, WOS0p...off-track slices.

Claims

1. A magnetic disk; a magnetic head that is positioned over tracks on the magnetic disk at a predetermined track pitch and writes data to and reads data from the tracks; a controller having an off-track write table, positioning the magnetic head, and registering in the off-track write table an address at which data is written on the track and a positioning error of the magnetic head with respect to the track at the address; when writing data to a 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 away from the first sector in a radial direction; Magnetic disk device.

2. the controller determines that the second sector is in an inactive state and sets a positioning error of the second sector to 0 when the second sector is in an unregistered state or when data is written to the second sector prior to data written to a sector between the first sector and the second sector; 2. The magnetic disk drive according to claim 1.

3. the controller corrects a positioning target position of the first sector based on a positioning error of a third sector located two tracks inward from the first sector and a positioning error of a fourth sector located two tracks outward from the first sector; 2. The magnetic disk drive according to claim 1.

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

5. The controller: When the third sector is in an unregistered state or when data is written to the third sector prior to data written to the sector between the first sector and the third sector, the third sector is determined to be in an inactive state, and a positioning error of the third sector is set to 0; If the fourth sector is in an unregistered state or if data has been written to the fourth sector prior to data being written to the sector between the first sector and the fourth sector, the fourth sector is determined to be in an inactive state, and a positioning error of the fourth sector is set to 0; when the third sector or the fourth sector is in an inactive state, correcting the positioning target position of the first sector so as to offset the first sector toward the sector determined to be in an inactive state out of the third sector and the fourth sector from the positioning target position corrected based on the correction amount; 5. The magnetic disk drive according to claim 4.

6. The controller: calculate an initial correction value, which is half the value obtained by adding a positioning error of a sector located two tracks away from the pair of sectors adjacent to the first sector in a circumferential direction perpendicular to the radial direction to a positioning error of a sector located two tracks away from the pair of sectors; calculating an auxiliary offset amount that is half the value obtained by adding an initial correction amount of one of the pair of sectors to an initial correction amount of the other of the pair of sectors; calculating an optimum correction amount value which is half the value obtained by adding the auxiliary offset amount to the correction amount; correcting the positioning target position of the first sector based on the optimum correction amount value; 5. The magnetic disk drive according to claim 4.

7. calculate an initial correction value, which is half the value obtained by adding the positioning error of the sector two tracks inside to the positioning error of the sector two tracks outside, for a predetermined number of sectors aligned in a first direction from the first sector and a predetermined number of sectors positioned in a second direction from the first sector opposite to the first direction in a circumferential direction perpendicular to the radial direction; calculating an optimal correction amount value by linearly combining the initial correction amount values ​​and the correction amounts in the predetermined number of sectors; correcting the positioning target position of the first sector based on the optimal correction amount value; 5. The magnetic disk drive according to claim 4.

8. The controller: calculating a threshold value for determining whether or not to stop a write operation to the first sector based on the positioning error of the third sector and the positioning error of the fourth sector; correcting a positioning target position of the first sector based on the threshold value; 4. The magnetic disk drive according to claim 3.

9. A method for controlling a magnetic disk device including a magnetic disk, a magnetic head positioned at a track on the magnetic disk at a predetermined track pitch, for writing data to the track and reading data from the track, and an off-track write table, comprising the steps of: positioning the magnetic head; registering an address at which data is written on the 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, a positioning target position of the first sector is corrected based on a positioning error of a second sector located two tracks away from the first sector in a radial direction; A method for controlling a magnetic disk device.

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