Magnetic disk device

Abstract

The invention relates to a magnetic disk device. According to one embodiment, in general, a magnetic disk device includes a disk, a read head, and a control unit. The control unit includes a read processing unit that executes a first read process of moving the read head to n1 radius positions and reading data of a track at each of the radius positions during a period in which the disk is rotated m1 circles, a comparison unit, and a determination unit that determines that the read head is moved to n1 radius positions during a period in which the disk is rotated m1 circles, and the read head is moved to n1 radius positions during a period in which the disk is rotated m1 circles. The comparison unit compares the qualities of a plurality of first signals read by the first reading process, and derives a first signal having the highest quality from among the plurality of first signals. The determination unit determines, from among the n1 radius positions, a radius position at which the first signal of the highest quality is derived as a first appropriate read position at which data of the track is appropriate to be read, where 1 < = m1 < n1.

Description

[0001] This application claims the priority of Japanese Patent Application No. 2023-213750 filed on December 19, 2023, and the entire content of the Japanese patent application is incorporated herein by reference. Technical Field

[0002] This embodiment generally relates to a disk device. Background Art

[0003] As disk devices, there are known: a Conventional Magnetic Recording (CMR) type (or conventional recording type) disk device that writes to a plurality of tracks at intervals in the radial direction of the disk, a Shingled Magnetic Recording (SMR) type (or Shingled Write Recording: SWR) disk device that overlaps and writes to a plurality of tracks in the radial direction of the disk, and a hybrid recording type disk device that selects and executes between the conventional recording type and the shingled recording type.

[0004] A disk device has a head including a write head and a read head. The write head and the read head are arranged at intervals in the circumferential direction of the disk. The closer the head seeks to the inner peripheral side or the outer peripheral side of the disk, the easier it is for the write head and the read head to be offset in the radial direction. Therefore, in a disk device, by arranging the read / write head offset at a position offset by a predetermined distance in the radial direction from the position of the read head when writing to a predetermined track on the disk using the write head, the data of the track can be read. Summary of the Invention

[0005] One embodiment includes a disk device having: a disk having tracks in a recording layer; a read head that reads data from the recording layer of the disk; and a control unit having: a read processing unit that executes a first read processing, which is a process of moving the read head to n1 radial positions that deviate from each other in the radial direction of the disk during a period in which the disk rotates m1 times, and reading the data of the tracks at each of the radial positions; a comparison unit that compares the quality of a plurality of first signals read by the first read processing and derives a first signal of the highest quality from the plurality of first signals; and a determination unit that determines the radial position at which the first signal of the highest quality is derived among the n1 radial positions as a first appropriate read position suitable for reading the data of the track, where 1 ≤ m1 < n1.

[0006] According to one embodiment of the present invention, a disk device capable of quickly finding an appropriate read position can be provided. Brief Description of the Drawings

[0007] Figure 1 It is a block diagram showing the configuration of the disk device of the comparative example.

[0008] Figure 2 It is a perspective view showing a part of the above disk device, and is a view showing multiple disks and multiple heads.

[0009] Figure 3 It is a schematic diagram showing an example of the configuration of multiple servo areas and multiple data areas of one disk of the above comparative example.

[0010] Figure 4 It is a schematic diagram showing an example of the configuration of the head relative to the disk of the above comparative example.

[0011] Figure 5 It is a view showing an example of the geometric configuration of the head relative to the track in the above comparative example when the center of gravity of the write head and the center of gravity of the read head are arranged in the circumferential direction, when the head is opposed to the innermost track, and when the head is opposed to the outermost track.

[0012] Figure 6 It is a view showing the positional relationship between the innermost track and the head during the write process and the read process, and the positional relationship between the outermost track and the head during the write process and the read process in the above comparative example.

[0013] Figure 7 It is a view showing the change in the position of the read head at multiple tracks in the above comparative example using a graph.

[0014] Figure 8 It is a view showing the change in the read bias displacement amount at multiple tracks in the above comparative example using a graph.

[0015] Figure 9 It is a view showing the positional relationship between the track and the head in the above comparative example in the case of three different read bias correction amounts.

[0016] Figure 10 It is a view showing the change in the amplitude of the signal read relative to the radial position of the read head in the above comparative example using a graph.

[0017] Figure 11 It is a view showing the change in the bit error rate of the signal read relative to the radial position of the read head in the above comparative example using a graph.

[0018] Figure 12 It is a block diagram showing an example of the head positioning control system of the above comparative example.

[0019] Figure 13This is a diagram for explaining the operation of the head when reading the data of a track while changing the above-mentioned read bias correction amount, showing (a) the state where the read head is fixed at the initial radius position and reading the data of the track, (b) the state where the read head is moved to the second radius position, (c) the state where the read head is fixed at the second radius position from the initial radius position and reading the data of the track, (d) the state where the read head is moved from the second radius position to the third radius position, and (e) the state where the read head is fixed at the final radius position and reading the data of the track.

[0020] Figure 14 These are diagrams respectively showing, by graphs, the changes in the bit error rate, the changes in the read bias correction amount, and the changes in the sector number of the target position in the above-mentioned comparative example when the read process, the seek operation, and the standby operation are repeatedly performed on the target track.

[0021] Figure 15 This is a block diagram showing the configuration of the disk device of the first embodiment.

[0022] Figure 16 This is a diagram for explaining the operation of the head when reading the data of a track while changing the above-mentioned read bias correction amount in the above-mentioned first embodiment, and is a diagram showing the state where the data of the track is read while moving the read head from the initial radius position to the final radius position.

[0023] Figure 17 These are diagrams respectively showing, by graphs, the changes in the bit error rate, the changes in the read bias correction amount, and the changes in the sector number of the target position in the above-mentioned first embodiment when the read process is performed on the target track.

[0024] Figure 18 This is a block diagram showing an example of the head positioning control system of the above-mentioned first embodiment.

[0025] Figure 19 This is a diagram showing, by a graph, the change of the read bias correction amount with respect to the position (radius position) of the target sector in the above-mentioned first embodiment, and is a diagram showing an example where the read bias correction amount changes in a straight-line track.

[0026] Figure 20 This is a flowchart for explaining a method for finding the first appropriate read bias correction amount applicable to the disk device of the above-mentioned first embodiment.

[0027] Figure 21It is a diagram showing the change of the read bias correction amount with respect to the position (radial position) of the target sector in the first modification of the first embodiment described above, and is a diagram showing an example in which the read start position is shifted three times in the circumferential direction and the read bias correction amount changes along the same straight track.

[0028] Figure 22 It is a diagram showing the change of the bit error rate, the change of the read bias correction amount, and the change of the sector number of the target position, respectively, when the read process, the seek operation, and the standby operation are repeatedly performed on the target track in the first modification of the first embodiment described above.

[0029] Figure 23 It is a diagram showing the change of the bit error rate, the change of the read bias correction amount, and the change of the sector number of the target position, respectively, when the process of reading the target track while moving the read head along a straight track in the first seek direction during one rotation of the disk and the process of reading the target track while moving the read head along a straight track in the second seek direction during one rotation of the disk are repeatedly performed in the second modification of the first embodiment.

[0030] Figure 24 It is a diagram showing the change of the read bias correction amount with respect to the position (radial position) of the target sector in the third modification of the first embodiment described above, and is a diagram showing an example in which the read bias correction amount changes along a straight track and rises to the right during one rotation of the disk, and then changes along a straight track and falls to the right.

[0031] Figure 25 It is a diagram showing the change of the bit error rate, the change of the read bias correction amount, and the change of the sector number of the target position, respectively, when the process of reading the target track while moving the read head along a straight track in the first seek direction during one rotation of the disk and then the process of reading the target track while moving the read head along a straight track in the second seek direction are repeatedly performed in the fourth modification of the first embodiment.

[0032] Figure 26 It is a diagram showing the change of the read bias correction amount with respect to the position (radial position) of the target sector in the fifth modification of the first embodiment described above, and is a diagram showing an example in which the read bias correction amount changes along a straight track and rises to the right during one rotation of the disk, then changes along a straight track and falls to the right, then changes along a straight track and rises to the right, and then changes along a straight track and falls to the right.

[0033] Figure 27 It is a graph showing the change of the read bias correction amount with respect to the position (radial position) of the target sector in Modification 6 of the above-described First Embodiment, and is a graph showing an example in which the read bias correction amount changes in a sinusoidal track.

[0034] Figure 28 It is a graph showing the change of the read bias correction amount with respect to the position (radial position) of the target sector in Modification 7 of the above-described First Embodiment using three graphs, and is a graph showing an example in which the read start position is shifted three times in the circumferential direction and the read bias correction amount changes in the same sinusoidal track respectively.

[0035] Figure 29 It is a graph showing the change of the read bias correction amount with respect to the position (radial position) of the target sector in Modification 8 of the above-described First Embodiment, and is a graph showing an example in which, during one rotation of the disk, the read bias correction amount changes in a sinusoidal track rising to the right, and then the read bias correction amount changes in a sinusoidal track falling to the right.

[0036] Figure 30 It is a graph showing the change in bit error rate, the change in read bias correction amount, and the change in the number of the target sector when the read process, the seek operation, and the standby operation are repeatedly performed on the target track in the disk device of the Second Embodiment, and is a graph showing an example in which the bit error rate is roughly measured in the first range and then precisely measured in the second range smaller than the first range.

[0037] Figure 31 It is a flowchart for explaining a method of finding the third appropriate read bias correction amount applicable to the disk device of the above-described Second Embodiment.

[0038] Figure 32 Following Figure 31 It is a flowchart for explaining the above method.

[0039] Figure 33 Following Figure 32 It is a flowchart for explaining the above method.

[0040] Explanation of Reference Numerals

[0041] 1…Disk device, 20…SPM, 24…VCM, 30…Arm, HD…Head, WHD…Write head, RHD…Read head, 60…MPU, 61…Read / write processing unit, 61a…Write processing unit, 61b…Read processing unit, 62…Comparison unit, 63…Judgment unit, 64…Read position averaging processing unit, 65…Signal quality averaging processing unit, 70…Volatile memory, 80…Buffer memory, 90…Non-volatile memory, 100…Host, 110…System controller, 120…Driver IC, 140…R / W channel, 14R…Read channel, 14W…Write channel, 150…HDC, DK…Disk, L…Recording layer, TR…Track, SC…Sector, P…Actuator, PXr…Radius position, PXropt…Appropriate read position, Xc…Read bias correction amount, Xcopt…Appropriate read bias correction amount, ID…Inner circumference, OD…Outer circumference, AP…Amplitude, ER…Bit error rate, PA…Acceleration period, PD…Deceleration period, d1…Radial direction, d2…Travel direction, d3…Rotation direction. Detailed implementation

[0042] Hereinafter, with reference to the drawings, a disk device 1 of a comparative example and each embodiment, and a method for finding an appropriate read position (appropriate read bias correction amount) will be described in detail.

[0043] (Comparative example)

[0044] First, the configuration of the disk device 1 of the comparative example will be described. Figure 1 It is a block diagram showing the configuration of the disk device 1 of the comparative example. In this comparative example, the disk device 1 is a hybrid recording type disk device. However, the disk device 1 may also be a shingled recording type disk device or a conventional recording type disk device.

[0045] As Figure 1 shown, the disk device 1 includes: a plurality of, for example, 1 to 11 disks (magnetic disks) DK as a recording medium, a spindle motor (SPM) 20 as a driving motor, a head stack assembly (hereinafter referred to as HSA) 22, a driver IC 120, a head amplifier integrated circuit (hereinafter referred to as head amplifier IC or preamplifier) 130, a volatile memory 70, a buffer memory (buffer) 80, a non-volatile memory 90, and a system controller 110 which is an integrated circuit in a single chip. In addition, the disk device 1 is connected to a host system (hereinafter simply referred to as host) 100.

[0046] Each disk DK is formed, for example, to have a diameter of 97 mm (3.8 inches) and has recording layers (magnetic recording layers) L on both of its surfaces. The disk DK has tracks in the recording layer L. The disk DK is mounted on the SPM20 and rotates by the drive of the SPM20. In addition, in this comparative example, the disk device 1 includes 1 to 11 disks DK, but the number of disks DK is not limited to this.

[0047] The arm 30 and a voice coil motor (hereinafter referred to as VCM) 24 constitute an actuator. The actuator can control the movement of the head HD mounted on the arm 30 to a predetermined position of the disk DK, that is, can perform a seek, by the drive of the VCM24. Although it will be described later, the disk device 1 includes a plurality of disks DK and a plurality of heads HD.

[0048] Regarding the disk DK, a user available user data area UU where data can be written and a system area SS where information necessary for system management is written are allocated to the area where data can be written. In addition, in the disk DK, a media cache area (or sometimes also referred to as a media cache) that temporarily holds data (or commands) transmitted from the host 100 etc. before writing to a predetermined area of the user data area UU may also be allocated.

[0049] The head HD records and reproduces information on the disk DK. The head HD has a slider as a main body and includes a write head WHD and a read head RHD mounted on the slider. The arm 30 supports the read head RHD and the write head WHD. The write head WHD writes data to the recording layer L of the disk DK. The read head RHD reads data from the tracks (data tracks) of the recording layer L of the disk DK.

[0050] The driver IC120 controls the drives of the SPM20 and the VCM24 according to the control of the system controller 110 (specifically, the MPU60 described later). The SPM20 supports and rotates a plurality of disks DK.

[0051] The head amplifier IC130 includes a read amplifier and a write driver. The read amplifier amplifies the read signal read from the disk DK and outputs it to the system controller 110 (specifically, the read / write (R / W) channel 140 described later). The write driver outputs a write current corresponding to the signal output from the R / W channel 140 to the head HD. Hereinafter, "writing data" may sometimes be referred to as "writing", "data writing", "writing process", etc. "Reading data" may sometimes be referred to as "reading", "data reading", "reading process", etc.

[0052] In addition, sometimes the write head WHD is simply referred to as the head HD, sometimes the read head RHD is simply referred to as the head HD, and sometimes the write head WHD and the read head RHD are collectively referred to as the head HD. Sometimes the central part (center of gravity) of the head HD is simply referred to as the head HD, sometimes the central part (center of gravity) of the write head WHD is simply referred to as the write head WHD, and sometimes the central part (center of gravity) of the read head RHD is simply referred to as the read head RHD.

[0053] Sometimes the "central part (center of gravity) of the write head WHD" is simply referred to as the "head HD", and sometimes the "central part (center of gravity) of the read head RHD" is simply referred to as the "head HD". Sometimes the expression "position the central part of the head HD at the center of the track of a predetermined track" is expressed as "position the head HD at a predetermined track", "configure the head HD at a predetermined track", "position the head HD at a predetermined track", etc.

[0054] The volatile memory 70 is a semiconductor memory in which the data stored is lost when the power supply is disconnected. The volatile memory 70 stores data required for processing in each part of the disk device 1. The volatile memory 70 is a random access memory (RAM: Random Access Memory). The volatile memory 70 is, for example, a DRAM (Dynamic Random Access Memory, dynamic random access memory). However, the volatile memory 70 can also be an SDRAM (Synchronous Dynamic Random Access Memory, synchronous dynamic random access memory).

[0055] The buffer memory 80 is a semiconductor memory that temporarily records data and the like transmitted and received between the disk device 1 and the host 100. In addition, the buffer memory 80 can also be integrally formed with the volatile memory 70. The buffer memory 80 is a volatile RAM. By way of example, the buffer memory 80 is a DRAM, an SRAM (Static Random Access Memory, static random access memory), an SDRAM, a FeRAM (Ferroelectric Random Access Memory, ferroelectric random access memory), an MRAM (Magnetoresistive Random Access Memory, magnetoresistive random access memory), etc.

[0056] The non-volatile memory 90 is a semiconductor memory that records the stored data even when the power supply is disconnected. The non-volatile memory 90 is, for example, a NAND-type flash read-only memory (Flash Read Only Memory: FROM). However, the non-volatile memory 90 can also be a NOR-type FROM.

[0057] The system controller (controller) 110 is implemented, for example, using a large-scale integrated circuit (LSI) called a System-on-a-Chip (SoC) in which multiple components are integrated on a single chip. The system controller 110 includes a Read / Write (R / W) channel 140, a Hard Disk Controller (HDC) 150, and a Microprocessor Unit (MPU) 60. The system controller 110 is electrically connected to a driver IC 120, a head amplifier IC 130, a volatile memory 70, a buffer memory 80, a non-volatile memory 90, and a host 100.

[0058] The R / W channel 140 performs signal processing of read data transmitted from the disk DK to the host 100 and write data transmitted from the host 100 according to an instruction from the MPU 60 described later. The R / W channel 140 includes a write channel 14W and a read channel 14R. The write channel 14W has a circuit or function for modulating write data. The read channel 14R has a circuit or function for measuring the quality of a plurality of signals obtained by a read process. The quality of the above signals is the amplitude of the signal or the Bit Error Rate (BER) of the signal. The R / W channel 140 is electrically connected to, for example, the head amplifier IC 130, the HDC 150, the MPU 60, etc.

[0059] The HDC 150 controls data transfer between the host 100 and the R / W channel 140 according to an instruction from the MPU 60 described later. The HDC 150 is electrically connected to, for example, the R / W channel 140, the MPU 60, the volatile memory 70, the buffer memory 80, the non-volatile memory 90, etc.

[0060] The MPU 60 is a control unit that controls each part of the disk device 1 and is the main controller. The MPU 60 controls the VCM 24 via the driver IC 120 and performs servo control for positioning the head HD. In addition, the MPU 60 controls the SPM 20 via the driver IC 120 to rotate the disk DK. The MPU 60 controls the write operation for writing data to the disk DK and selects a storage destination for the write data transmitted from the host 100. In addition, the MPU 60 controls the read operation for reading data from the disk DK and controls the processing of the read data transmitted from the disk DK to the host 100. The MPU 60 is connected to each part of the disk device 1. The MPU 60 is electrically connected to, for example, the driver IC 120, the R / W channel 140, the HDC 150, etc.

[0061] The MPU 60 includes a read / write processing unit 61, a comparison unit 62, a determination unit 63, and a signal quality averaging processing unit 65. The MPU 60 executes the processing of the above units, such as the read / write processing unit 61, the comparison unit 62, the determination unit 63, the signal quality averaging processing unit 65, etc., on the firmware. In addition, the MPU 60 may also include the above units as circuits.

[0062] The read / write processing unit 61 includes a write processing unit 61a and a read processing unit 61b. According to a command from the host 100, the write processing unit 61a controls the write processing of writing data to the recording layer L of the disk DK, and the read processing unit 61b controls the read processing of reading data from the recording layer L of the disk DK. The read / write processing unit 61 controls the VCM 24 via the driver IC 120, positions the head HD at a target position (predetermined radius position) on the disk DK, and executes the read processing or the write processing.

[0063] The comparison unit 62 can compare the quality of a plurality of signals read by the read processing and derive the signal with the highest quality from the plurality of signals.

[0064] The determination unit 63 can determine the radius position at which the highest quality signal is derived among a plurality of radius positions on one track of the recording layer L as an appropriate read position suitable for reading data of the above track.

[0065] The signal quality averaging processing unit 65 can derive a plurality of averaged qualities. Each averaged quality is a quality obtained by averaging the quality of a plurality of signals read multiple times by the read processing at one radius position on the track of the recording layer L.

[0066] Figure 2 It is a perspective view showing a part of the disk device 1, and is a view showing a plurality of disks DK and a plurality of heads HD.

[0067] As Figure 2 shown, in the circumferential direction of the disk DK, the direction in which the disk DK rotates is called the rotation direction d3. In addition, in the Figure 2 example shown, the rotation direction is indicated by the counterclockwise direction, but it may also be the opposite direction (clockwise direction). In addition, the traveling direction d2 of the head HD with respect to the disk DK is opposite to the rotation direction d3. The traveling direction d2 is the direction in which the head HD sequentially writes and reads data with respect to the disk DK in the circumferential direction, that is, the direction in which the head HD travels with respect to the disk DK in the circumferential direction.

[0068] The disk device 1 includes i disks DK1 to DKi and j heads HD1 to HDj. In this comparative example, the number of heads HD is twice the number of disks DK (j = 2 × i).

[0069] The disks DK1 to DKi are coaxially arranged and overlapped with intervals therebetween. The disks DK1 to DKi have the same diameter. Here, terms such as "same", "identical", "consistent", "equivalent", etc. of course include the meaning of being completely the same, and also include the meaning of having differences to the extent that they can be regarded as substantially the same. In addition, the diameters of the disks DK1 to DKi may also be different from each other.

[0070] Each disk DK has recording layers L on both sides. For example, disk DK1 has a first recording layer La1 and a second recording layer Lb1 on the opposite side of the first recording layer La1. Disk DK2 has a first recording layer La2 and a second recording layer Lb2 on the opposite side of the first recording layer La2. Disk DKi has a first recording layer Lai and a second recording layer Lbi on the opposite side of the first recording layer Lai. Each first recording layer La is sometimes also referred to as a surface or a recording surface. Each second recording layer Lb is sometimes also referred to as a back surface or a recording surface.

[0071] Each recording layer L has a user data area UU and a system area SS.

[0072] The first recording layer La1 has a user data area UUa1 and a system area SSa1. The second recording layer Lb1 has a user data area UUb1 and a system area SSb1. The first recording layer La2 has a user data area UUa2 and a system area SSa2. The second recording layer Lb2 has a user data area UUb2 and a system area SSb2. The first recording layer Lai has a user data area UUai and a system area SSai. The second recording layer Lbi has a user data area UUbi and a system area SSbi.

[0073] The track sandwiched by double dotted lines in the figure in the user data area UUa1 (the first recording layer La1) is set as track TRa1. The track on the opposite side of track TRa1 in the user data area UUb1 (the second recording layer Lb1) is set as track TRb1.

[0074] The track sandwiched by double dotted lines in the figure in the user data area UUa2 (the first recording layer La2) is set as track TRc1. The track on the opposite side of track TRc1 in the user data area UUb2 (the second recording layer Lb2) is set as track TRd1.

[0075] The track sandwiched by double dotted lines in the figure in the user data area UUai (the first recording layer Lai) is set as track TRe1. The track on the opposite side of track TRe1 in the user data area UUbi (the second recording layer Lbi) is set as track TRf1.

[0076] In this comparative example, tracks TaR1, TRb1, TRc1, TRd1, TRe1, and TRf1 are located on the same cylinder.

[0077] Head HD faces disk DK. In this comparative example, one head HD faces each recording layer L of disk DK. For example, head HD1 faces the first recording layer La1 of disk DK1, writes data to the first recording layer La1, and reads data from the first recording layer La1. Head HD2 faces the second recording layer Lb1 of disk DK1, writes data to the second recording layer Lb1, and reads data from the second recording layer Lb1.

[0078] Head HD3 faces the first recording layer La2 of disk DK2, writes data to the first recording layer La2, and reads data from the first recording layer La2. Head HD4 faces the second recording layer Lb2 of disk DK2, writes data to the second recording layer Lb2, and reads data from the second recording layer Lb2. Head HDj - 1 faces the first recording layer Lai of disk DKi, writes data to the first recording layer Lai, and reads data from the first recording layer Lai. Head HDj faces the second recording layer Lbi of disk DKi, writes data to the second recording layer Lbi, and reads data from the second recording layer Lbi.

[0079] In addition, a predetermined position in the radial direction d1 of disk DK is sometimes referred to as a radial position, and a predetermined position in the circumferential direction of disk DK is sometimes referred to as a circumferential position. Sometimes, the radial position and the circumferential position are simply collectively referred to as a position. The radial position corresponds to the distance from the rotation center of disk DK to a predetermined radial position, the distance from the innermost circumference of disk DK to a predetermined radial position, the distance from the outermost circumference of disk DK to a predetermined radial position, the distance from a predetermined radial position of disk DK to another radial position, and the like.

[0080] Figure 3 is a schematic diagram showing an example of the configuration of a plurality of servo areas SV and a plurality of data areas DTR on one disk DK of this comparative example. As Figure 3 shown, in the radial direction d1 of disk DK, the direction toward the outer circumference of disk DK is called the outer direction (outer side), and the direction opposite to the outer direction is called the inner direction (inner side).

[0081] In Figure 3 it, the user data area UU is divided into an inner circumferential area IR located in the inner direction, an outer circumferential area OR located in the outer direction, and a middle circumferential area MR located between the inner circumferential area IR and the outer circumferential area OR.

[0082] The disk DK has a plurality of servo areas SV and a plurality of data areas DTR. The plurality of servo areas SV may, for example, also extend radially in the radial direction of the disk DK and be discretely arranged at a predetermined interval in the circumferential direction. The plurality of servo areas SV may, for example, also extend linearly from the inner circumference to the outer circumference and be discretely arranged at a predetermined interval in the circumferential direction. The plurality of servo areas SV may, for example, also extend spirally from the inner circumference to the outer circumference and be discretely arranged at a predetermined interval in the circumferential direction. Additionally, the plurality of servo areas SV may, for example, also be arranged in an island shape in the radial direction and be discretely arranged while changing the predetermined interval in the circumferential direction.

[0083] Hereinafter, one servo area SV in a predetermined track may sometimes be referred to as a "servo sector". In addition, the "servo area SV" may sometimes be referred to as the "servo sector SV". The servo sector contains servo data. Hereinafter, the "configuration etc. of several servo data constituting the servo sector" may sometimes be referred to as a "servo pattern". In addition, the "servo data written to the servo sector" may sometimes be referred to as the "servo sector".

[0084] The plurality of data areas DTR are respectively arranged between the plurality of servo areas SV. For example, the data area DTR corresponds to the area between two consecutive servo areas SV in the circumferential direction. Hereinafter, one data area DTR in a predetermined track may sometimes be referred to as a "data sector". In addition, the "data area DTR" may sometimes be referred to as the "data sector DTR". The data sector contains user data. In addition, the "user data written to the data sector" may sometimes be referred to as the "data sector". Sometimes the "data sector" is also referred to as "user data". Additionally, the "pattern composed of several data" may sometimes be referred to as a "data pattern". In Figure 2 In the example shown, the data pattern of the predetermined track is composed of a plurality of servo data (servo sectors) and a plurality of user data (data sectors).

[0085] The servo area SV has a plurality of partition servo areas ZSV, etc. In addition, the servo area SV may also include, in addition to the partition servo area ZSV, an area including a gap (the deviation of the circumferential positions of two partition servo areas), an area including servo data, and a data area DTR, etc. The plurality of partition servo areas ZSV are discretely arranged along the radial direction. The plurality of partition servo areas ZSV each extend in the radial direction.

[0086] Sometimes, one partition servo area (servo area) ZSV in a predetermined track is also referred to as a "partition servo sector" or a "servo sector". In addition, sometimes the "partition servo area (servo area) ZSV" is also referred to as the "partition servo sector ZSV" or the "servo sector ZSV". Sometimes, the "servo data written to the partition servo sector" is also referred to as the "partition servo sector" or the "servo sector". Hereinafter, sometimes the "configuration, etc. of several servo data constituting the partition servo sector" is also referred to as the "partition servo pattern" or the "servo pattern". Hereinafter, sometimes one servo area SV in a predetermined track is also referred to as a "partition pattern sector".

[0087] In addition, sometimes the "servo area SV" is also referred to as the "partition pattern sector". Sometimes, at least one data, etc. written to the partition pattern sector is also referred to as the "partition pattern sector". The partition pattern sector includes at least one partition servo sector. Hereinafter, sometimes the "data pattern of the partition pattern sector" is also referred to as the "partition data pattern".

[0088] In Figure 3 In the example shown, the servo area SV has partition servo areas ZSV0, ZSV1, and ZSV2. The partition servo areas ZSV0, ZSV1, and ZSV2 are arranged in a staggered manner in the radial direction. The partition servo areas ZSV0, ZSV1, and ZSV2 may also be arranged in a stepped manner in the radial direction.

[0089] The partition servo area ZSV2 is located on the inner circumferential side of the partition servo area ZSV1. The partition servo area ZSV0 is located on the outer circumferential side of the partition servo area ZSV1. For example, the partition servo area ZSV2 is arranged from the inner circumferential area IR to the middle circumferential area MR, the partition servo area ZSV1 is arranged from the inner circumferential area IR to the outer circumferential area OR, and the partition servo area ZSV0 is arranged from the middle circumferential area MR to the outer circumferential area OR. Hereinafter, sometimes a predetermined area in the radial direction where a plurality of partition servo areas ZSV are arranged in the circumferential direction in a predetermined servo area SV is also referred to as a partition servo boundary area, a double servo area, or a double partition servo area ZB.

[0090] In Figure 3In the example shown, the main servo region SVO and the sub-servo region SVE are alternately arranged at intervals in the circumferential direction. For example, in the circumferential direction, one sub-servo region SVE is arranged between two main servo regions SVO arranged continuously at intervals. For example, when all servo regions SV of the disk DK are assigned sequentially consecutive numbers, the main servo region SVO corresponds to the odd-numbered servo regions SV, and the sub-servo region SVE corresponds to the even-numbered servo regions SV. In addition, in the circumferential direction, two or more sub-servo regions SVE may be arranged between two main servo regions SVO arranged continuously at intervals.

[0091] The main servo region SVO and the sub-servo region SVE may also be constituted only by servo regions that read and demodulate servo data as a whole (hereinafter sometimes referred to as normal servo regions). Hereinafter, "reading and demodulating servo data" is sometimes referred to as "servo reading". The main servo region SVO and the sub-servo region SVE may also be constituted by a normal servo region and a servo region that reads the circumferential range of servo data that is smaller in the circumferential direction than the circumferential range of servo data read in the normal servo region (hereinafter sometimes referred to as a short servo region).

[0092] A media cache M is allocated to the disk DK. However, the media cache M may not be configured on the disk DK.

[0093] By using the above-mentioned multiple servo data, the head HD can be positioned in such a way as to obtain a predetermined off-track amount.

[0094] Figure 4 It is a schematic diagram showing an example of the configuration of the head HD of this comparative example with respect to the disk DK.

[0095] As Figure 4 shown, track numbers (cylinder numbers) are assigned to concentric tracks (data tracks) formed from the outer circumference OD to the inner circumference ID of the disk DK. When the number of tracks is Nc, the track number C is from 0 to Nc - 1 (C = 0, 1, 2,..., Nc - 1).

[0096] Each track has a plurality of sectors. Sector numbers are assigned in the traveling direction d2 of the head HD. When the number of sectors is Ns, the sector number S is from 0 to Ns - 1 (S = 0, 1, 2,..., Ns - 1).

[0097] When the head HD floats on the rotating disk DK, the distance between the head HD and the recording layer L (surface) of the disk DK is maintained within a certain range. The head HD has a write head WHD and a read head RHD. The write head WHD and the read head RHD are arranged in the circumferential direction ( Figure 3)。Data on the track written (recorded) by the write head WHD can be read (reproduced) by the read head RHD.

[0098] Figure 5 FIG. is an example showing the geometric configuration of the head HD with respect to the track in the case where the center of gravity WC of the write head WHD and the center of gravity RC of the read head RHD are arranged in the circumferential direction, the case where the head HD faces the innermost track, and the case where the head HD faces the outermost track in this comparative example. In addition, each single dotted line in the figure indicates the center (track center) of the corresponding track.

[0099] As Figure 5 shown, in the seek direction, the write head WHD has a width (core width) Ww, and the read head RHD has a width (core width) Wr. The head HD is moved in the seek direction (substantially inward or outward direction) by an actuator and is controlled to be positioned on the target track. Servo information indicating the radius position on the disk DK is recorded in each sector. By reading the servo information using the read head RHD, the radius position of the head HD on the disk DK can be detected. Although it will be described later, the above seek direction is the first seek direction (e.g., substantially inward direction) or the second seek direction (e.g., substantially outward direction).

[0100] Since the above actuator is generally a rotary actuator, the head HD has a skew angle with respect to the track according to the radius position of the head HD on the disk DK. Generally, the write head WHD and the read head RHD are arranged in the rotation direction of the disk DK.

[0101] For example, there is a case where when the head HD is positioned on the track with the track number C being Ct, the write head WHD is neither offset toward the outer peripheral side nor toward the inner peripheral side with respect to the read head RHD. When the head HD is positioned on the outer peripheral track of the disk DK, the write head WHD is offset toward the outer peripheral side with respect to the read head RHD. On the contrary, when the head HD is positioned on the inner peripheral track of the disk DK, the write head WHD is offset toward the inner peripheral side with respect to the read head RHD.

[0102] Figure 6 FIG. is a diagram showing the positional relationship between the innermost track, i.e., track TRNc - 1, and the head HD during the write process and the read process, and the positional relationship between the outermost track, i.e., track TR0, and the head HD during the write process and the read process in this comparative example.

[0103] On the Figure 6 left side, the positional relationship between the head HD and the track TRNc - 1 during the write operation and the read operation at the track TRNc - 1 with the track number C being Nc - 1 is shown. The head HD shown by the solid line indicates the position during the write operation, and the head HD shown by the dotted line indicates the position during the read operation.

[0104] When a track TRNc-1 with a track width Wt is formed by a write head WHD, a read head RHD is positioned at a radial position PXw that is offset by a distance Xs from the write head WHD toward the outer circumference OD side (radial direction d1) due to a skew angle. In a direction parallel to the radial direction d1, the distance from the reference position to the read head RHD during the write operation is Xw. In addition, the above-mentioned reference position is, for example, the center of the track TR0 (track center).

[0105] To read the data of the track TRNc-1, it is necessary to position the read head RHD at a radial position PXr that is offset by a distance Xs from the position during the write operation toward the inner circumference ID side. In a direction parallel to the radial direction d1, the distance from the reference position to the read head RHD during the read operation is Xr. In the above case, the distance Xs is the read bias displacement amount.

[0106] At Figure 6 the right side shows the positional relationship between the head HD and the track TR0 during the write operation and the read operation at the track TR0 with a track number C of 0. The head HD shown by the solid line represents the position during the write operation, and the head HD shown by the dashed line represents the position during the read operation.

[0107] When a track TR0 with a track width Wt is formed by a write head WHD, a read head RHD is positioned at a radial position PXw that is offset by a distance Xs from the write head WHD toward the inner circumference ID side (the opposite direction of the radial direction d1) due to a skew angle.

[0108] To read the data of the track TR0, it is necessary to position the read head RHD at a radial position PXr that is offset by a distance Xs from the position during the write operation toward the outer circumference OD side.

[0109] Figure 7 is a graph showing the change in the position of the read head RHD at multiple tracks TR in this comparative example. On the Figure 7 horizontal axis, the right direction corresponds to the inner direction of the disk DK, and the left direction corresponds to the outer direction of the disk DK. On the Figure 7 vertical axis, the upward direction corresponds to the inner direction of the disk DK, and the downward direction corresponds to the outer direction of the disk DK.

[0110] As Figure 7 shown, the solid line represents the radial position PXw of the read head RHD during the write process, and the dashed line represents the radial position PXr of the read head RHD during the read process. It can be seen that the positional relationship between the radial position PXw of the read head RHD during the write process and the radial position PXr of the read head RHD during the read process is reversed on the inner circumference ID side and the outer circumference OD side.

[0111] Figure 8This is a graph showing the variation of the read bias displacement amount Xs at multiple tracks TR in this comparative example. In Figure 8 On the horizontal axis of Figure 8 , the right direction corresponds to the inner direction of the disk DK, and the left direction corresponds to the outer direction of the disk DK. In

[0112] As Figure 8 shown, the read bias displacement amount Xs can be obtained based on the difference between the distance Xr and the distance Xw (Xs = Xr - Xw). In this comparative example, the read bias displacement amount Xs is calculated by the MPU 60 (for example, the read processing unit 61b). However, the read bias displacement amount Xs can also be obtained without calculation. In this case, a memory such as the non-volatile memory 90 can also have a table containing information on the read bias displacement amount Xs.

[0113] By positioning the read head RHD at the radius position PXr that is offset by the read bias displacement amount Xs from the radius position PXw at the time of writing according to the skew angle in this way, reading can be performed at the center position of the track TR.

[0114] However, there are individual differences in the positional relationship between the write head WHD and the read head RHD in the head HD, especially their positional relationship in the seek direction. Therefore, it is not necessarily the same among individuals. For example, due to certain reasons including manufacturing deviations, a bias sometimes occurs between the write head WHD and the read head RHD. In addition, the magnetic field distribution generated by the write head WHD is uneven in the radial direction d1 of the disk DK due to the aforementioned skew angle and individual differences. Therefore, it often occurs that the center position of the track width Wt of the track TR is not a read position suitable for reading the data of the track TR. Therefore, in addition to the read bias displacement amount Xs with respect to the radius position of the target track due to the skew angle as described above, it is also necessary to obtain an appropriate value Xcopt (for example, the optimal value) of the read bias correction amount Xc for correcting it.

[0115] Figure 9 This is a graph showing the positional relationship between the track TR (track TRCt) and the head HD in this comparative example in the case of three different read bias correction amounts Xc. In addition, it is assumed that the read bias displacement amount Xs with respect to the target track due to the skew angle as described above is zero, and it is not shown in the figure.

[0116] As Figure 9As shown, when positioning the read head RHD at the radius position PXw during writing and performing the writing process, the write head WHD forms a track TR having a track width Wt substantially equal to the width Ww. At this time, when the read head RHD is positioned at an appropriate read position PXropt offset by an appropriate read bias correction amount Xcopt from the radius position PXw due to the deviation in the radial direction d1 between the aforementioned write head WHD and the read head RHD or the like, an appropriate read operation can be performed. In order to obtain the appropriate read bias correction amount Xcopt, a read operation is performed at the radius positions PXr[i] to which several points of read bias correction amounts Xc[i] are applied, and the radius position that results in an appropriate (good) read state is obtained. When performing a read operation on the track TR at k points, the read operation can be performed at k radius positions PXr[0], PXr[1], PXr[2],..., PXr[k - 1].

[0117] Figure 10 is a graph showing the change in the amplitude of the signal read in this comparative example with respect to the radius position of the read head RHD.

[0118] As Figure 10 shown, a graph shows the distribution (profile) of the amplitude AP[i] of the signal when reading data on the track TR at the radius positions PXr[i] corresponding to the read bias correction amounts Xc[i] (read bias correction amounts Xc[0], Xc[1], Xc[2],..., Xc[k - 1]) for k points. Here, the read bias correction amount Xc[i] at which the amplitude AP[i] of the signal read by the read head RHD becomes the maximum can be obtained, and this is set as the appropriate read bias correction amount Xcopt.

[0119] In Figure 10 the example, the highest quality signal is the signal among the multiple signals for which the amplitude AP[i] becomes the maximum. Preferably, the highest quality signal is the signal among the multiple signals for which the amplitude AP[i] becomes the maximum value.

[0120] Figure 11 is a graph showing the change in the bit error rate (BER) of the signal read in this comparative example with respect to the radius position of the read head RHD.

[0121] As Figure 11As shown, instead of measuring the amplitude of the read signal, the bit error rate of the read signal can be measured. The distribution of the bit error rate ER[i] of the signal when reading data on the read track TR at the respective radius positions PXr[i] of the read bias correction amount Xc[i] with respect to k points is shown in a graph. Here, the read bias correction amount Xc[i] at which the bit error rate ER[i] of the signal read by the read head RHD becomes the minimum can be obtained, and this is set as the appropriate read bias correction amount Xcopt.

[0122] In Figure 11 the example, the highest quality signal is the signal with the minimum bit error rate ER[i] among the multiple signals. Preferably, the highest quality signal is the signal with an extremely small bit error rate ER[i] among the multiple signals.

[0123] In the method for finding the track center in this comparative example, first, data for one round is written to the target track TR. Then, by fixing the read head RHD at a predetermined radius position and reading the data of the track TR for one round, the read channel 14R measures a plurality of bit error rates related to the signal, and the signal quality averaging unit 65 derives the averaged bit error rate obtained by averaging the plurality of bit error rates. In the subsequent finding method, the averaged bit error rate is also derived while changing the radius position of the fixed read head RHD.

[0124] Then, the comparison unit 62 derives the minimum averaged bit error rate from the plurality of averaged bit error rates, and the determination unit 63 determines the radius position at which the minimum averaged bit error rate is derived as the appropriate read position.

[0125] Figure 12 is a block diagram showing an example of the positioning control system SY of the head HD in this comparative example.

[0126] As Figure 12 shown, the disk device 1 has a positioning control system SY for the head HD. The positioning control system SY includes a transducer (Transducer: Physical target Transducer For Writing (physical target transducer for writing)) TD, a generator (Generator: Read Offset Generator) ROG1, a generator (Generator: Read Offset Generator) ROG2, an adder AD1, an adder AD2, a subtractor SU1, a controller (Controller) CL, and an actuator P.

[0127] Converter TD, generator ROG1, generator ROG2, adder AD1, adder AD2, subtractor SU1, and controller CL are included in, for example, head amplifier IC130, system controller 110, etc. Actuator P is composed of, for example, arm 30, VCM 24, etc. Subtractor SU1, controller CL, and actuator P constitute a feedback system.

[0128] The disk device 1 is instructed by the host 100 to read the address (C, H, S) of the target sector. Here, regarding the target sector to be read, C is the track number (cylinder number), H is the head number, and S is the sector number. Then, the converter TD converts the above address into a distance Xw corresponding to the track number C and outputs it. The generator ROG1 converts the above address into a read bias displacement amount Xs caused by the skew angle (or track number C, radius position, etc.) and outputs it. The generator ROG2 converts the above address into a read bias correction amount Xc based on reasons other than the skew angle and outputs it.

[0129] As described using Figure 10 and Figure 11 as mentioned above, the read bias correction amount Xc can be obtained by measuring the read bias distribution of the read signal in the pre-factory test process, etc., and appropriate read bias correction amounts Xcopt, etc., can be derived. Information on the read bias displacement amount Xs and the read bias correction amount Xc is input to the adder AD1, and the adder AD1 outputs information that adds the read bias displacement amount Xs and the read bias correction amount Xc (Xs + Xc) to the adder AD2. The adder AD2 outputs information on the distance Xr obtained by adding the information (Xs + Xc) after adding the read bias displacement amount Xs and the read bias correction amount Xc to the distance Xw (Xr = Xw + Xs + Xc) to the subtractor SU1.

[0130] To measure the above read bias distribution, it can be achieved by reading the data of one track TR while changing the read bias correction amount Xc for k read bias correction amounts Xc[0], Xc[1], Xc[2], …, Xc[k - 1] respectively and measuring the quality (amplitude or bit error rate) of the read signal. The radius position PXr of the read target position at this time can be determined based on the information of the distance Xr.

[0131] The physical radius position Yr of the read head RHD can be obtained by reading and demodulating the servo information on the disk DK. The subtractor SU1 outputs the positioning error e, which is the information obtained by subtracting the physical radius position Yr from the distance Xr (e = Xr - Yr), to the controller CL. In order to achieve stable positioning control by the controller CL, the controller CL can obtain the control amount U by performing gain compensation and phase compensation on the positioning error e. Further, by driving the actuator P with the control amount U as the input, the read head RHD can be controlled to be positioned at the read target position (radius position PXr).

[0132] Figure 13 This is a diagram for explaining the operation of the head HD when reading the data of the track TRCt while changing the read bias correction amount Xc in this comparative example. In Figure 13 , the states are shown as follows: (a) the state where the read head RHD is fixed at the initial radius position and reads the data of the track TRCt; (b) the state where the read head RHD moves to the second radius position; (c) the state where the read head RHD is fixed at the second radius position from the initial radius position and reads the data of the track TRCt; (d) the state where the read head RHD moves from the second radius position to the third radius position; (e) the state where the read head RHD is fixed at the final radius position and reads the data of the track TRCt.

[0133] As Figure 13 shown, it is possible to know the position and operation of the read head RHD on the disk DK when measuring the amplitude or bit error rate of the read signal. In the radial direction d1, Figure 13 illustrates three tracks TR, namely the track TRCt and the tracks TRCt-1 and TRCt+1 before and after the track TRCt. In the circumferential direction, Figure 13 illustrates five sectors SCNs-2, SCNs-1, SC0, SC1, SC2 with the sector numbers S being 0, and the sector numbers Ns-2, Ns-1, 1, 2 before and after the sector number S of 0.

[0134] In the track TRCt, while changing the variable i in the order of 0, 1, 2, …, k-1 and changing the read bias correction amount Xc[i], the read head RHD moves successively to a plurality of radius positions PXr[i]. The radius positions PXr[i] are represented by concentric single dotted lines.

[0135] As Figure 13As shown in (a), first, set the variable i to 0, fix the read bias correction amount as Xc[0], and start the read process from sector SC0 of track TRCt. As shown by the solid arrow, the read process is performed in the order of sector SC0, sector SC1, sector SC2 until sector SCNs - 1, and the read process of the data of one - round amount of track TRCt ends.

[0136] The initial radius position PXr of the read head RHD, that is, the radius position PXrs, is a position that is at a distance Xr[0] from the reference position (Xr[0]=Xw + Xs+Xc[0]).

[0137] As Figure 13 As shown in (b), when starting the read process at radius position PXr[1] next, as shown by the dashed arrow, a bias seek operation from radius position PXr[0] to radius position PXr[1] needs to be performed. Therefore, instead of immediately performing the read process, a seek operation and a standby operation (rotation waiting operation) are performed. In addition, the dashed arrow represents both the seek operation and the standby operation. Here, during the seek operation and the standby operation, the disk DK rotates one week.

[0138] As Figure 13 As shown in (c), then, fix the read head RHD at the radius position PXr[1] from sector SC0 of track TRCt as shown by the solid arrow and start the read process again.

[0139] After that, the read process, the seek operation, and the standby operation are repeatedly performed until the variable i reaches k - 1. After fixing the read head RHD at the radius position PXr[k - 1] and performing the read process, the data read of track TRCt ends.

[0140] The final radius position PXr of the read head RHD, that is, the radius position PXre, is a position that is at a distance Xr[k - 1] from the reference position (Xr[k - 1]=Xw + Xs+Xc[k - 1]).

[0141] Through the above various operations, a more accurate distribution of the amplitudes of the signals at multiple radius positions PXr[i] (which are also multiple read positions) or a more accurate distribution of the bit error rates of the signals can be obtained.

[0142] Figure 14 These are graphs showing the changes in the bit error rate ER[i], the changes in the read bias correction amount Xc[i], and the changes in the sector number S of the target position when the read process, the seek operation, and the standby operation are repeatedly performed on the target track TR in this comparative example. Starting from the uppermost section, the operation mode, the measured bit error rate ER of the signal, the read bias correction amount Xc, and the sector number S are shown.

[0143] As Figure 14 shown, the read bias correction amount is set to Xc[0]. During the period Trot when the disk DK rotates one revolution, the read channel 14R measures the bit error rate of the signal read from the data of the sector SC0 of the track TR to the data of the sector SCNs-1.

[0144] The signal quality averaging unit 65 averages a plurality of bit error rates ER[0] obtained during the period when the read bias correction amount is set to Xc[0], and derives the averaged bit error rate.

[0145] Next, by changing the read bias correction amount from Xc[0] to Xc[1], a seek operation (bias seek) and a standby operation are performed. During the standby operation, the read channel 14R and the like are in an idle state.

[0146] In the subsequent read process, the read bias correction amount is fixed to Xc[1]. During the period Trot when the disk DK rotates one revolution, the read channel 14R measures the bit error rate of the signal read from the data of the sector SC0 of the track TR to the data of the sector SCNs-1.

[0147] The signal quality averaging unit 65 averages a plurality of bit error rates ER[1] obtained during the period when the read bias correction amount is set to Xc[1], and derives the averaged bit error rate.

[0148] By repeatedly performing the read process, the seek operation, and the standby operation on the target track TR until the variable i reaches k-1, the acquisition of a plurality of averaged bit error rates is completed.

[0149] However, in Figure 14 the method for finding the track center shown, in order to obtain the distribution of the bit error rates at a plurality of radius positions PXr[i], a time period of 2×k×Trot is required. For example, in the disk device 1 with 7200 rpm, the period Trot is 8.3 msec (Trot = 8.3 msec). In addition, assume k = 10. Then, in order to perform the read process at 10 radius positions PXr to obtain the distribution of the bit error rates, a time period of 166 msec is required (2×k×Trot = 2×10×8.3 [msec]).

[0150] According to the disk device 1 configured as described above and the method of finding the appropriate read position PXropt, for example, if the time period for finding the track center during the manufacturing process increases, the total time required for adjusting the disk device 1 during manufacturing increases, which may lead to an increase in manufacturing costs. In particular, in the perpendicular recording type disk device 1, the radius position PXr varies greatly with respect to the radius position PXw according to the track pitch. Since the process of obtaining the appropriate read offset correction amount Xcopt (track center finding) is necessary, the time period for obtaining the appropriate read offset correction amount Xcopt has a great impact on the manufacturing period.

[0151] Sometimes, the track center is found not only before actually using the disk device 1 but also after actually using the disk device 1. In this case, it is also desirable that the time period required for finding the track center is short.

[0152] (First Embodiment)

[0153] Next, the configuration of the disk device 1 according to the first embodiment will be described. Figure 15 It is a block diagram showing the configuration of the disk device 1 according to the first embodiment. Except for the configuration described in this first embodiment, the disk device 1 is configured in the same manner as the disk device 1 of the above comparative example.

[0154] As Figure 15 shown, the MPU 60 further includes a read position averaging processing unit 64. The configuration and function of the read position averaging processing unit 64 will be described later.

[0155] The read processing unit 61b can execute a first read process, which is a process of moving the read head RHD to n1 radius positions PXr that are mutually deviated in the radius direction d1 of the disk DK during the period when the disk DK rotates m1 times, and reading the data of the track TR at each radius position PXr.

[0156] The read channel 14R can measure the quality of a plurality of first signals read by the first read process. In addition, the quality of the first signal is the above-mentioned amplitude or bit error rate.

[0157] The comparison unit 62 can compare the quality of a plurality of first signals read by the first read process, and derive the first signal with the highest quality from the plurality of first signals.

[0158] The determination unit 63 can determine the radius position PXr (PXropt1) when the first signal with the highest quality is derived among the above n1 radius positions PXr as the first appropriate read position PXropt1 suitable for reading the data of the track TR.

[0159] In this first embodiment, the disk device 1 satisfies the relationship of the following formula 1.

[0160] 1 ≤ m1 < n1 … Formula 1

[0161] For example, the above value m1 is 1 (m1 = 1). The above value n1 corresponds to the above value k and is, for example, 10 (n1 = 10). Since it is not the case that m1 ≥ n1, the first appropriate read position PXropt1 can be searched for at high speed. In other words, compared with the above comparative example, the time period for obtaining the first appropriate read offset correction amount Xcopt1 (searching for the track center) can be shortened.

[0162] Moreover, when reading data of the track TR, the read processing unit 61b can move the read head RHD to the first appropriate read position PXropt1 and read the data of the track TR at the first appropriate read position PXropt1.

[0163] The write processing unit 61a can move the read head RHD to the standby position as the radius position PXw and perform a write process of writing data to the track TR through the write head WHD.

[0164] When the first appropriate read position PXropt1 is a position offset from the standby position (radius position PXw) and data of the track TR is read, the read processing unit 61b can move the read head RHD to the first appropriate read position PXropt1 offset from the standby position and read the data of the track TR at the first appropriate read position PXropt1.

[0165] On the other hand, when the first appropriate read position PXropt1 coincides with the standby position (radius position PXw) and data of the track TR is read, the read processing unit 61b can move the read head RHD to the first appropriate read position PXropt1 as the standby position and read the data of the track TR at the first appropriate read position PXropt1.

[0166] As described above, when reading data of the track TR, it is only necessary to perform offset correction as needed starting from the write process of writing to the track TR.

[0167] Figure 16 This is a diagram for explaining the operation of the head HD when reading data of the track TRCt while changing the read offset correction amount Xc[i], and is a diagram showing a state of reading data of the track TRCt while moving the read head RHD from the initial radius position PXrs to the final radius position PXre.

[0168] As Figure 16 shown, it is possible to know the position and operation of the read head RHD on the disk DK when measuring the amplitude or bit error rate of the read signal. And Figure 13Similarly, in the radial direction d1, Figure 16 shows three tracks TRCt-1, TRCt, and TRCt+1. Similarly, Figure 13 in the circumferential direction, Figure 16 shows five sectors SCNs-2, SCNs-1, SC0, SC1, and SC2.

[0169] In track TRCt, while sequentially changing the variable i to 0, 1, 2, …, k-1 and changing the read bias correction amount Xc[i], the read head RHD sequentially moves to multiple radial positions PXr[i]. The radial positions PXr[i] are represented by concentric single-dot dash lines.

[0170] First, set the variable i to 0, set the read bias correction amount to Xc[0], and start the read process from sector SC0 of track TRCt. Then, as shown by the solid arrows, while gradually increasing the read bias correction amount Xc at a certain ratio as the sector number S increases, sequentially perform the read process, set the read bias correction amount Xc to Xce(Xc[k-1]), and perform the read process on the final sector SCNs-1. By performing the read process in this way, it is possible to measure the quality (e.g., bit error rate) of the signals in the range from the radial position PXrs to the radial position PXre during one rotation of the disk DK.

[0171] For example, when the number of sectors SC (the above value k) in track TRCt is 500, it is possible to measure the quality of the signals at 500 points in the range from the radial position PXrs to the radial position PXre. And in Figure 16 the operation example, the disk device 1 also satisfies the relationship of the above formula (1 ≤ m1 < n1).

[0172] In addition, the timing for setting the read bias correction amount Xc to Xce(Xc[k-1]) is not limited to the timing for performing the read process on sector SCNs-1, and various modifications can be made. For example, the timing for setting the read bias correction amount Xc to Xce(Xc[k-1]) can also be the timing for performing the read process on sector SCNs-4.

[0173] In addition, the read channel 14R may not measure the quality of the signals read for each sector SC. For example, the read channel 14R may measure the quality of the signals read for every multiple sectors SC.

[0174] Figure 17The diagrams respectively show changes in the bit error rate ER[i], changes in the read offset correction amount Xc[i], and changes in the sector number S of the target position when the target track TRCt is read in the first embodiment. Figure 17 Compared with the comparative example Figure 14 correspond.

[0175] like Figure 17 As shown, as the target sector SC is shifted in the direction of travel d2 such as sectors SC0, SC1, and SC2, the radial position PXr[i] changes from the radial position PXrs to the radial position PXre. Therefore, the distribution of the quality (bit error rate) of the read signal can be obtained during one rotation Trot of the disk DK.

[0176] Figure 18 This is a block diagram showing an example of the positioning control system SY of the head HD according to the first embodiment.

[0177] like Figure 18 As shown, the positioning control system SY includes a generator (Generator: Read Offset Generator) ROG3 instead of the generator ROG2. The information of the sector number S of the read target sector SC is input to the generator ROG3. The generator ROG3 converts the sector number S into a read offset correction amount Xc based on the sector number S and outputs it.

[0178] For example, the read offset correction amount Xc depends only on the sector number S. In this case, the read offset correction amount Xc for the sector SC0 of the track TR0 is the same as the read offset correction amount Xc for the sector SC0 of the track TRNc-1.

[0179] Figure 19 This is a diagram showing a change in the read bias correction amount Xc with respect to the position (radial position) of the target sector SC in the first embodiment using a graph, and is a diagram showing an example of changing the read bias correction amount Xc along a linear trajectory. Figure 19 The read offset correction amount Xc can be obtained by calculation. However, the read offset correction amount Xc may not be obtained by calculation. In this case, a memory such as the nonvolatile memory 90 may have a table including information on the read offset correction amount Xc.

[0180] like Figure 19 As shown, when executing the first reading process, the reading processing unit 61b makes the reading head RHD seek in the first seek direction (in this example, the substantially inner direction) at a constant speed. The n1 radial positions PXr are arranged at equal intervals in the radial direction d1. When executing the first reading process, the reading processing unit 61b can read the data of the track TR at a constant time interval.

[0181] During one rotation of the disk DK, the read bias correction amount Xc changes (increases) linearly. The read bias correction amount Xc when reading the data of the read sector SC0 becomes Xcs (Xc[0]), and the read bias correction amount Xc when reading the data of the read sector SCNs-1 becomes Xce (Xc[k-1]).

[0182] Based on the distribution of the bit error rate of the signal obtained by reading the data of the track TR for one read amount, the Sopt1 as the sector number S and the first appropriate read bias correction amount Xcopt1 as the read bias correction amount Xc when the bit error rate becomes the minimum can be obtained. Among them, it is preferable that the sector number Sopt1 and the first appropriate read bias correction amount Xcopt1 are the values when the bit error rate becomes extremely small.

[0183] Figure 20 It is a flowchart for explaining a method of finding the first appropriate read bias correction amount Xcopt1 applicable to the disk device 1 of the first embodiment.

[0184] As Figure 20 shown, when starting the method of finding the first appropriate read bias correction amount Xcopt1 for the track TR, first, in step STa1, the read processing unit 61b initializes the sector number S of the target position to 0 (S = 0).

[0185] Next, in step STa2, according to the read bias correction amount Xc(S) obtained from the generator ROG3, the read processing unit 61b moves the read head RHD to the radius position PXr(S) within the first range and positions it. Then, in step STa3, the read channel 14R measures the bit error rate ER(S).

[0186] The radius position PXr(S) is a position that is away from the reference position by a distance Xr(S) (Xr(S) = Xw + Xs + Xc(S)). The first range is a range having a width in the radial direction d1 and is a range from the radius position PXrs to the radius position PXre.

[0187] Then, in step STa4, the read processing unit 61b increments (adds one) the sector number S of the target position. Next, in step STa5, the read processing unit 61b determines whether the sector number S of the target position has exceeded the final sector number Ns-1. If the sector number S has not exceeded the sector number Ns-1 (S ≤ Ns-1), it moves to step STa2 and repeatedly executes the processing of steps STa2 to STa5.

[0188] On the other hand, when it is determined in step STa5 that the sector number S of the target position exceeds the sector number Ns - 1 (S = Ns), the measurement of the bit error rate ER in the first range ends, and the process moves to step STa6. In step STa6, the comparison unit 62 compares the bit error rates ER of the plurality of first signals read by the first read process, and derives the first signal with the minimum (preferably extremely small) bit error rate ER from the plurality of first signals. Then, it is possible to find the sector number S, i.e., Smin, when the first signal with the minimum bit error rate ER is derived.

[0189] Next, in step STa7, the determination unit 63 determines that the read bias correction amount Xc[Smin] when reading the sector SCmin with the sector number S of Smin is the first appropriate read bias correction amount Xcopt1 (Xcopt1 = Xc[Smin]). Thus, the method for finding the first appropriate read bias correction amount Xcopt1 for the track TR ends.

[0190] According to the disk device 1 of the first embodiment configured as described above and the method for finding the first appropriate read position PXropt1, the disk device 1 includes a disk DK having a track TR in the recording layer L, a read head RHD, and an MPU 60. The MPU 60 includes a read processing unit 61b, a comparison unit 62, and a determination unit 63.

[0191] The read processing unit 61b can execute a first read process, which is a process of moving the read head RHD to n1 radius positions PXr that are mutually offset in the radius direction d1 of the disk DK during m1 rotations of the disk DK, and reading the data of the track TR at each radius position PXr.

[0192] The comparison unit 62 can compare the quality of the plurality of first signals read by the first read process, and derive the first signal with the highest quality from the plurality of first signals.

[0193] The determination unit 63 can determine the radius position PXr (PXropt1) when the first signal with the highest quality is derived among the above n1 radius positions PXr as the first appropriate read position PXropt1 suitable for reading the data of the track TR.

[0194] 1 ≤ m1 < n1. Therefore, in the first embodiment, it is possible to find the first appropriate read position PXropt1 at high speed, and it is possible to shorten the time period for obtaining the first appropriate read bias correction amount Xcopt1 (searching for the track center).

[0195] (Modification Example 1 of the First Embodiment)

[0196] Next, the configuration of the disk device 1 of modification example 1 of the first embodiment will be described.Figure 21 This is a diagram showing the change in the position (radial position) of the read bias correction amount Xc with respect to the target sector SC in the first modification example 1, and is a diagram showing an example in which the read start position is shifted three times in the circumferential direction and the read bias correction amount Xc changes along the same straight track. Figure 22 This is a diagram showing, respectively, the change in the bit error rate ER, the change in the read bias correction amount Xc, and the change in the sector number of the target position when the read process, the seek operation, and the standby operation are repeatedly performed on the target track TR in the first modification example 1.

[0197] Except for the configuration described in the first modification example 1, the disk device 1 is configured in the same manner as the disk device 1 in the first embodiment. In the first modification example 1, an appropriate read position PXropt can be found at high speed, and the sector dependency of the bit error rate can be averaged.

[0198] As Figure 21 and Figure 22 shown, the read processing unit 61b performs the first read process in the same manner as in the first embodiment ( Figure 19 ). In the first read process, the read processing unit 61b first sets the read bias correction amount Xc to Xcs (Xc[0]) and reads the data of the sector SC0, and finally sets the read bias correction amount Xc to Xce (Xc[k - 1]) and reads the data of the sector SCNs - 1.

[0199] Based on the distribution of the bit error rate of the signal obtained by reading the data of the track TR for one revolution, the Sopt1 as the sector number S and the first appropriate read bias correction amount Xcopt1 as the read bias correction amount Xc when the bit error rate becomes the minimum can be obtained.

[0200] Following the first read process, the read processing unit 61b sequentially performs a seek operation, a rotational waiting operation, and a second read process. The second read process is the following process: During the period when the disk DK rotates m2 weeks, the read head RHD is seeked in the first seek direction in the same manner as in the first read process, and the read head RHD is moved to n2 radial positions PXr that are mutually deviated in the radial direction d1, and the data of the track TR is read at each radial position PXr.

[0201] In the first modification example 1, the disk device 1 satisfies the relationship of the following formula 2.

[0202] 1 ≤ m2 < n2… Formula 2

[0203] The operation of seeking the read head RHD during the second read process is the same as the operation of seeking the read head RHD during the first read process. In the first modification example 1, n1 = n2 and m1 = m2.

[0204] In the second read process, the read processing unit 61b first sets the read bias correction amount Xc to Xcs (Xc[0]) and reads the data of the sector SC{(2 / 3)(Ns - 1)}, and finally sets the read bias correction amount Xc to Xce (Xc[k - 1]) and reads the data of the sector SC{(2 / 3)(Ns - 1)-1}.

[0205] The position (sector SC0) where the data of the track TR is first read in the first read process and the position (sector SC{(2 / 3)(Ns - 1)}) where the data of the track TR is first read in the second read process deviate from each other in the circumferential direction. As described above, it can be seen that in each of the first read process and the second read process, the read bias correction amount Xc changes along the same straight track.

[0206] The comparison unit 62 can also compare the qualities of the multiple second signals read by the second read process, and derive the second signal with the highest quality from the multiple second signals.

[0207] The determination unit 63 can also determine the radius position PXr when deriving the second signal with the highest quality among the n2 radius positions PXr as the second appropriate read position PXropt2a suitable for reading the data of the track TR.

[0208] For example, based on the distribution of the bit error rate of the signals obtained by reading the data of one week's worth of the track TR in the second read process, the Sopt2a as the sector number S and the second appropriate read bias correction amount Xcopt2a as the read bias correction amount Xc when the bit error rate becomes the minimum can be obtained.

[0209] The read position averaging processing unit 64 can derive the averaged position, which is the position obtained by averaging the first appropriate read position PXropt1 and the second appropriate read position PXropt2a in the radial direction d1. Thus, when reading the data of the track TR, the read processing unit 61b can move the read head RHD to the above-mentioned averaged position and read the data of the track TR at the above-mentioned averaged position. It is easy to position the read head RHD at a more appropriate radius position PXr than the above-mentioned first embodiment and perform the read process, and it is easy to obtain a higher quality signal through the read process.

[0210] The number of times of performing the read process on one track is not limited to 2 times, and it can also be performed 3 times or more. In the first modification example, 3 read processes including the above-mentioned first read process and the above-mentioned second read process are performed.

[0211] After the second read process, the read processing unit 61b sequentially performs a seek operation, a rotation wait operation, and a third read process. The third read process is as follows: During the period when the disk DK rotates m (for example, rotates m2) times, the read head RHD is seeked in the first seek direction in the same manner as in the second read process, and the read head RHD is moved to n (for example, n2) radial positions PXr that are mutually deviated in the radial direction d1. The data of the track TR is read at each radial position PXr (1 ≤ m < n).

[0212] The operation of seeking the read head RHD during the third read process is the same as the operation of seeking the read head RHD during the first read process and the second read process.

[0213] In the third read process, the read processing unit 61b first sets the read offset correction amount Xc to Xcs (Xc[0]) and reads the data of the sector SC{(1 / 3)(Ns - 1)}, and finally sets the read offset correction amount Xc to Xce (Xc[k - 1]) and reads the data of the sector SC{(1 / 3)(Ns - 1) - 1}.

[0214] The position (sector SC0) where the data of the track TR is first read in the first read process, the position (sector SC{(2 / 3)(Ns - 1)}) where the data of the track TR is first read in the second read process, and the position (sector SC{(1 / 3)(Ns - 1)}) where the data of the track TR is first read in the third read process are mutually deviated in the circumferential direction. As described above, it can be seen that in each of the first read process, the second read process, and the third read process, the read offset correction amount Xc changes along the same straight track.

[0215] The comparison unit 62 can also compare the quality of a plurality of third signals read through the third read process, and derive the third signal with the highest quality from the plurality of third signals. The determination unit 63 can also determine the radial position PXr at the time of deriving the third signal with the highest quality among the n radial positions PXr as the third appropriate read position PXropt2b suitable for reading the data of the track TR.

[0216] For example, based on the distribution of the bit error rate of the signal obtained by reading the data of one week's worth of the track TR in the third read process, the Sopt2b as the sector number S and the third appropriate read offset correction amount Xcopt2b as the read offset correction amount Xc when the bit error rate becomes the minimum can be obtained.

[0217] The read position averaging unit 64 can derive an averaged position in the radial direction d1 of the first appropriate read position PXropt1, the second appropriate read position PXropt2a, and the third appropriate read position PXropt2b, that is, the averaged position. Since the distribution of the bit error rates of the amounts of three generation systems (pedigrees) can be obtained, an appropriate read bias correction amount Xcopt (appropriate read position PXropt) that is free from sector number dependence can be obtained.

[0218] Thus, when reading the data of the track TR, the read processing unit 61b can move the read head RHD to the above-mentioned averaged position and read the data of the track TR at the above-mentioned averaged position. It is easy to position the read head RHD at a radius position PXr more appropriate than the above-mentioned first embodiment and perform the read processing, and it is easy to obtain a higher quality signal through the read processing.

[0219] The sector SC0, the sector SC{(1 / 3)(Ns - 1)}), and the sector SC{(2 / 3)(Ns - 1)}) are arranged at equal intervals in the circumferential direction. There may be a case where the total number Ns of sectors SC of the track TR cannot be divided by 3. In this case, in the second read processing, the read processing unit 61b first reads the data of the sector SC with the sector number S having an integer value close to the value of {(2 / 3)(Ns - 1)}, and in the third read processing, the read processing unit 61b first reads the data of the sector SC with the sector number S having an integer value close to the value of {(1 / 3)(Ns - 1)}.

[0220] In addition, different from the first modification example 1, the read start positions may be shifted in the circumferential direction to perform four or more read processes. Since the number of generation systems of the distribution of the bit error rate can be increased, the effect of averaging the appropriate read position PXropt can be improved. However, it should be noted that the longer the number of read processes performed on one track TR, the longer the time period for searching for the appropriate read position PXropt.

[0221] In the first modification example 1, the same effect as the above-mentioned first embodiment can also be obtained. In addition, since multiple read processes can be performed with the measurement positions shifted in the circumferential direction, the sector dependence of the signal quality can be averaged.

[0222] (Second modification example of the first embodiment)

[0223] Next, the configuration of the disk device 1 according to the second modification example of the first embodiment will be described. Figure 23FIG. is a diagram showing changes in the bit error rate ER, changes in the read bias correction amount Xc, and changes in the sector number S of the target position in the case where the process of reading the target track TR while moving the read head RHD in a straight track in the first seek direction during one rotation of the disk DK and the process of reading the target track TR while moving the read head RHD in a straight track in the second seek direction during one rotation of the disk DK are repeatedly performed in the second modification example.

[0224] Except for the configuration described in the second modification example, the disk device 1 is configured in the same manner as the disk device 1 of the first embodiment. In the first modification example, an appropriate read position PXropt can be searched for at high speed, the read process can be continuously performed multiple times without a standby operation, and the effect of averaging the appropriate read position PXropt can be improved.

[0225] As Figure 23 shown, the read processing unit 61b performs the first read process in the same manner as in the first embodiment ( Figure 19 ). In the first read process, the read processing unit 61b first sets the read bias correction amount Xc to Xcs (Xc[0]) and reads the data of the sector SC0, and finally sets the read bias correction amount Xc to Xce (Xc[k - 1]) and reads the data of the sector SCNs - 1.

[0226] Based on the distribution of the bit error rate of the signal obtained from the data of the track TR for one read, the Sopt1 as the sector number S and the first appropriate read bias correction amount Xcopt1 as the read bias correction amount Xc when the bit error rate becomes the minimum can be obtained.

[0227] The read processing unit 61b can execute the second read process after the first read process. In the second modification example, the read processing unit 61b executes the second read process and the third read process after the first read process, and executes the read process multiple times. The second read process is the following process: During m2 rotations of the disk DK, the read head RHD is uniformly seeked in the second seek direction opposite to the first seek direction (in this example, the substantially outer direction), the read head RHD is moved to n2 radial positions that are deviated from each other in the radial direction d1, and the data of the track TR is read at each radial position PXr.

[0228] In the second modification example, the disk device 1 satisfies the relationship of the above formula 2 (1 ≤ m2 < n2).

[0229] The operation of seeking the read head RHD during the second read process is the same as the operation during the first read process except that the seek direction is the second seek direction. In the second modification example, n1 = n2 and m1 = m2.

[0230] In the second read process, the read processing unit 61b first sets the read offset correction amount Xc to Xce (Xc[k - 1]) and reads the data of the sector SC0, and finally sets the read offset correction amount Xc to Xcs (Xc[0]) and reads the data of the sector SCNs-1.

[0231] Based on the above situation, the range of the radial direction d1 measured in the second read process is the same as the range of the radial direction d1 measured in the first read process. That is, the radial position PXr where the data of the track TR is finally read in the first read process and the radial position PXr where the data of the track TR is first read in the second read process are the radial position PXre and are the same. The radial position PXr where the data of the track TR is first read in the first read process and the radial position PXr where the data of the track TR is finally read in the second read process are the radial position PXrs and are the same.

[0232] Different from the above Modification 1, the second read process can be implemented after the first read process without interposing a seek operation and a standby operation. The radial position PXr at which the read head RHD moves does not change discontinuously. Since the measurement of the quality (e.g., bit error rate) of the signal for reading the data of the track TR can be performed continuously rather than intermittently, the above quality can be measured multiple times in a short time.

[0233] The comparison unit 62 can also compare the quality of a plurality of second signals read by the second read process and derive the second signal with the highest quality from the plurality of second signals.

[0234] The determination unit 63 can also determine the radial position PXr when deriving the second signal with the highest quality among the n2 radial positions PXr as the second appropriate read position PXropt2a suitable for reading the data of the track TR.

[0235] The read position averaging processing unit 64 can derive the averaged position, which is the position obtained by averaging the first appropriate read position PXropt1 and the second appropriate read position PXropt2a in the radial direction d1. Thus, when reading the data of the track TR, the read processing unit 61b can move the read head RHD to the above averaged position and read the data of the track TR at the above averaged position. It is easy to position the read head RHD at a radial position PXr more appropriate than the above first embodiment and perform the read process, and it is easy to obtain a signal with higher quality through the read process.

[0236] The number of read processes performed on one track is not limited to 2 times, and can also be 3 times or more. In this Modification 2, including the above first read process and the above second read process, 6 read processes are performed.

[0237] In addition, the time period for each read process is not limited to the period Trot of one rotation of the disk DK, and can be less than the above period Trot or exceed the above period Trot.

[0238] Moreover, the time periods for each read process are the same, but they can also be different from each other.

[0239] In this second modification example, the same effects as those of the above-described first embodiment can also be obtained. In addition, since the number of generating systems of the distribution of the bit error rate can be increased, the effect of averaging the appropriate read position PXropt can be improved.

[0240] (Modification Example 3 of the First Embodiment)

[0241] Next, the configuration of the disk device 1 according to the third modification example of the first embodiment will be described. Figure 24 FIG. is a diagram showing the change of the read bias correction amount Xc with respect to the position (radial position PXr) of the target sector SC in this third modification example, and is an example showing that during one rotation of the disk DK, the read bias correction amount Xc changes upward to the right along a straight track and then changes downward to the right along a straight track. Except for the configuration described in this third modification example, the disk device 1 is configured in the same manner as the disk device 1 of the above-described second modification example.

[0242] As Figure 24 shown, during the period Trot of one rotation of the disk DK, both the first read process in which the read head RHD performs a uniform seek in the first seek direction and the second read process in which the read head RHD performs a uniform seek in the second seek direction can be performed. The read head RHD reciprocates between the radial position PXrs and the radial position PXre.

[0243] Based on the distribution of the bit error rate of the signal obtained by the first read process performed during the first half rotation period of the disk DK, the sector number Sopt1 and the first appropriate read bias correction amount Xcopt1 when the bit error rate becomes the minimum can be obtained. Based on the distribution of the bit error rate of the signal obtained by the second read process performed during the remaining half rotation period of the disk DK, the sector number Sopt2a and the second appropriate read bias correction amount Xcopt2a when the bit error rate becomes the minimum can be obtained.

[0244] In this third modification example, the same effects as those of the above-described first embodiment can also be obtained. In addition, the appropriate read bias correction amount Xcopt (appropriate read position PXropt) can be obtained multiple times in a short time.

[0245] (Modification Example 4 of the First Embodiment)

[0246] Next, the configuration of the disk device 1 of modification example 4 of the first embodiment will be described. Figure 25 It is a diagram showing the changes in the bit error rate, the changes in the read bias correction amount Xc, and the changes in the sector number of the target position in the case where the process of reading the target track TR while moving the read head RHD in a straight track in the first seek direction and then reading the target track while moving the read head RHD in a straight track in the second seek direction is repeated during one rotation of the disk DK. Except for the configuration described in this modification example 4, the disk device 1 is configured in the same manner as the disk device 1 of the above-described modification example 2.

[0247] As Figure 25 shown, the technology of this modification example 4 is equivalent to the combination of the technology of the above-described modification example 2 ( Figure 23 ) and the technology of the above-described modification example 3 ( Figure 24 ). During the period Trot of one rotation of the disk DK, both the first read process of performing uniform seek of the read head RHD in the first seek direction and the second read process of performing uniform seek of the read head RHD in the second seek direction are performed. Moreover, the number of read processes performed on one track TR is 3 or more times, for example, 12 times (6 round trips).

[0248] In this modification example 4, the same effects as those of the above-described modification example 2 and the above-described modification example 3 can also be obtained.

[0249] (Modification Example 5 of the First Embodiment)

[0250] Next, the configuration of the disk device 1 of modification example 5 of the first embodiment will be described. Figure 26 It is a diagram showing the change of the read bias correction amount Xc with respect to the position (radial position PXr) of the target sector SC in this modification example 5, and is an example showing that during one rotation of the disk DK, the read bias correction amount Xc changes linearly and rises to the right, then the read bias correction amount Xc changes linearly and falls to the right, then the read bias correction amount Xc changes linearly and rises to the right, and then the read bias correction amount Xc changes linearly and falls to the right. Except for the configuration described in this modification example 5, the disk device 1 is configured in the same manner as the disk device 1 of the above-described modification example 3.

[0251] As Figure 26 shown, 3 or more read processes can also be performed during the period Trot of one rotation of the disk DK. In this modification example 5, 4 (2 round trips) read processes are performed.

[0252] In the fifth modification example, the same effect as that of the third modification example described above can also be obtained.

[0253] (Sixth Modification Example of the First Embodiment)

[0254] Next, the configuration of the disk device 1 according to the sixth modification example of the first embodiment will be described. Figure 27 FIG. is a diagram showing the change of the read bias correction amount Xc with respect to the position (radial position PXr) of the target sector SC in this sixth modification example, and is a diagram of an example in which the read bias correction amount Xc changes in a sinusoidal track. Except for the configuration described in this sixth modification example, the disk device 1 is configured in the same manner as the disk device 1 of the first embodiment described above.

[0255] As Figure 27 shown, when performing the first read process, the read process unit 61b causes the read head RHD to seek in the first seek direction (in this example, the inward direction), but does not cause the read head RHD to seek at a constant speed. The period of performing the first read process includes a first acceleration period PA1 as the start period and a first deceleration period PD1 as the last period. The read process unit 61b causes the read head RHD to seek while gradually increasing the speed in the first seek direction during the first acceleration period PA1. The read process unit 61b causes the read head RHD to seek while gradually decreasing the speed in the first seek direction during the first deceleration period PD1.

[0256] In this sixth modification example, instead of causing the read head RHD to seek at a constant speed, the read head RHD is caused to seek in an ease-in-out manner. Since a sharp change in the speed of the read head RHD during seeking can be suppressed, the risk of the resonance frequency of the excitation mechanism system can be reduced.

[0257] In addition, in this sixth modification example, n1 radial positions PXr are provided at equal intervals in the radial direction d1. Therefore, the read process unit 61b reads the data of the track TR while gradually shortening the time interval during the first acceleration period PA1. The read process unit 61b reads the data of the track TR while gradually lengthening the time interval during the first deceleration period PD1.

[0258] In this sixth modification example, the same effect as that of the first embodiment described above can also be obtained. In addition, the period of performing the first read process may also include a first constant-speed period in which the read head RHD seeks at a constant speed between the first acceleration period PA1 and the first deceleration period PD1. In this case, the risk of the resonance frequency of the excitation mechanism system can also be reduced.

[0259] (Seventh Modification Example of the First Embodiment)

[0260] Next, the configuration of the disk device 1 according to the seventh modification example of the first embodiment will be described.Figure 28 This is a diagram showing the change in the position (radial position PXr) of the read bias correction amount Xc with respect to the target sector SC in the seventh modification example, and shows an example in which the read start position is shifted three times in the circumferential direction, and the read bias correction amount Xc changes in the same sinusoidal track. Except for the configuration described in the seventh modification example, the disk device 1 is configured in the same manner as the disk device 1 in the sixth modification example described above.

[0261] As Figure 28 shown, the technology of the seventh modification example 7 corresponds to the combination of the technology of the above modification example 1 ( Figure 21 ) and the technology of the above modification example 6 ( Figure 27 ). The read processing unit 61b performs the first read processing in the same manner as the read processing unit 61b in the sixth modification example ( Figure 27 ). In the first read processing, the read processing unit 61b first sets the read bias correction amount Xc to Xcs (Xc[0]) and reads the data of the sector SC0, and finally sets the read bias correction amount Xc to Xce (Xc[k - 1]) and reads the data of the sector SCNs - 1.

[0262] Based on the distribution of the bit error rate of the signal obtained by reading the data of the track TR for one week, the Sopt1 as the sector number S and the first appropriate read bias correction amount Xcopt1 as the read bias correction amount Xc when the bit error rate becomes the minimum can be obtained.

[0263] After the first read processing, the read processing unit 61b sequentially performs a seek operation, a rotation wait operation, and a second read processing. The second read processing is the following processing: During the rotation of the disk DK for m2 weeks, the read head RHD is seeked in the first seek direction in the same manner as in the first read processing, and the read head RHD is moved to n2 radial positions PXr that are mutually deviated in the radial direction d1, and the data of the track TR is read at each radial position PXr. In the seventh modification example, the disk device 1 satisfies the relationship of the above formula 2 (1 ≤ m2 < n2).

[0264] The operation of seeking the read head RHD during the second read processing is the same as the operation of seeking the read head RHD during the first read processing in the sixth modification example. In the seventh modification example, n1 = n2 and m1 = m2.

[0265] In the second read processing, the read processing unit 61b first sets the read bias correction amount Xc to Xcs (Xc[0]) and reads the data of the sector SC{(2 / 3)(Ns - 1)}, and finally sets the read bias correction amount Xc to Xce (Xc[k - 1]) and reads the data of the sector SC{(2 / 3)(Ns - 1) - 1}.

[0266] The position (sector SC0) where the data of the track TR is first read in the first reading process and the position (sector SC{(2 / 3)(Ns - 1)}) where the data of the track TR is first read in the second reading process deviate from each other in the circumferential direction. As described above, it can be seen that in each of the first reading process and the second reading process, the read bias correction amount Xc changes along the same sinusoidal track.

[0267] The comparison unit 62 can also compare the quality of a plurality of second signals read by the second reading process, and derive the second signal with the highest quality from the plurality of second signals.

[0268] The determination unit 63 can also determine the radius position PXr when deriving the second signal with the highest quality among the n2 radius positions PXr as the second appropriate reading position PXropt2a suitable for reading the data of the track TR.

[0269] For example, according to the distribution of the bit error rate of the signals obtained by reading the data of one full rotation of the track TR in the second reading process, the sector number Sopt2a and the second appropriate read bias correction amount Xcopt2a when the bit error rate becomes the minimum can be obtained.

[0270] The read position averaging processing unit 64 can derive the averaged position, which is the position obtained by averaging the first appropriate reading position PXropt1 and the second appropriate reading position PXropt2a in the radial direction d1. Thus, when reading the data of the track TR, the reading processing unit 61b can move the read head RHD to the above-mentioned averaged position and read the data of the track TR at the above-mentioned averaged position. It is easy to position the read head RHD at a more appropriate radius position PXr than the above-mentioned modification example 6 and perform the reading process, and it is easy to obtain a higher quality signal through the reading process.

[0271] The number of times of performing the reading process on one track is not limited to 2 times, and can also be 3 times or more. In this modification example 7, including the above-mentioned first reading process and the above-mentioned second reading process, 3 reading processes are performed. In the 3 reading processes, the read bias correction amount Xc changes along the same easing-in / easing-out track.

[0272] After the second reading process, the reading processing unit 61b sequentially performs a seek operation, a rotation waiting operation, and a third reading process. The third reading process is the same as the above-mentioned modification example 1 ( Figure 21 ) except for the read bias correction amount Xc.

[0273] The comparison unit 62 can also compare the quality of a plurality of third signals read by the third reading process, and derive the third signal with the highest quality from the plurality of third signals.

[0274] The determination unit 63 can also determine the radius position PXr at which the third signal with the highest quality is derived among the n radius positions PXr as the third appropriate reading position PXropt2b suitable for reading the data of the track TR.

[0275] For example, based on the distribution of the bit error rate of the signals obtained by reading the data of one full rotation of the track TR in the third reading process, the Sopt2b as the sector number S and the third appropriate reading bias correction amount Xcopt2b as the reading bias correction amount Xc when the bit error rate becomes the minimum can be obtained.

[0276] The reading position averaging processing unit 64 can derive the averaged position, which is the position obtained by averaging the first appropriate reading position PXropt1, the second appropriate reading position PXropt2a, and the third appropriate reading position PXropt2b in the radial direction d1. An appropriate reading bias correction amount Xcopt (appropriate reading position PXropt) without sector number dependency can be obtained.

[0277] Thereby, when reading the data of the track TR, the reading processing unit 61b can move the reading head RHD to the above-mentioned averaged position and read the data of the track TR at the above-mentioned averaged position.

[0278] In this modification 7, the same effects as those of the above-mentioned modification 1 and the above-mentioned modification 6 can also be obtained.

[0279] (Modification 8 of the First Embodiment)

[0280] Next, the configuration of the disk device 1 of modification 8 of the first embodiment will be described. Figure 29 This is a diagram showing the change of the reading bias correction amount Xc with respect to the position (radius position PXr) of the target sector SC in this modification 8, and is an example showing that during one rotation of the disk DK, the reading bias correction amount Xc changes in a sinusoidal orbit rising to the right, and then the reading bias correction amount Xc changes in a sinusoidal orbit falling to the right. Except for the configuration described in this modification 8, the disk device 1 is configured in the same manner as the disk device 1 of the above-mentioned modification 6.

[0281] As Figure 29 shown, the technology of this modification 8 is equivalent to the technology of the above-mentioned modification 3 ( Figure 24 ) and the technology of the above-mentioned modification 6 ( Figure 27) combination of technologies. It is also possible to perform both the first reading process in which the reading head RHD performs a seek in a fade-in / fade-out manner in the first seek direction and the second reading process in which the reading head RHD performs a seek in a fade-in / fade-out manner in the second seek direction during one rotation Trot of the disk DK. The reading head RHD reciprocates between the radius position PXrs and the radius position PXre.

[0282] Specifically, the reading process unit 61b performs the second reading process after the first reading process. The second reading process is the following process: During the period of m2 rotations of the disk DK, the reading head RHD performs a seek in the second seek direction, and the reading head RHD is moved to n2 radius positions PXr that are mutually offset in the radial direction d1, and the data of the track TR is read at each radius position PXr. In this modification example 8, the disk device 1 satisfies the relationship of the above formula 2 (1 ≤ m2 < n2). In this modification example 8, n1 = n2 and m1 = m2.

[0283] The period of performing the second reading process includes a second acceleration period PA2 as the start period and a second deceleration period PD2 as the last period. The reading process unit 61b causes the reading head RHD to perform a seek while gradually increasing the speed in the second seek direction during the second acceleration period PA2. The reading process unit 61b causes the reading head RHD to perform a seek while gradually decreasing the speed in the second seek direction during the second deceleration period PD2.

[0284] In this modification example 8, the n2 radius positions PXr are arranged at equal intervals in the radial direction d1. Therefore, the reading process unit 61b reads the data of the track TR while gradually shortening the time interval during the second acceleration period PA2. The reading process unit 61b reads the data of the track TR while gradually lengthening the time interval during the second deceleration period PD2.

[0285] Based on the distribution of the bit error rate of the signal obtained through the first reading process during the first half rotation period of the disk DK, the sector number Sopt1 and the first appropriate reading bias correction amount Xcopt1 when the bit error rate becomes the minimum can be obtained. Based on the distribution of the bit error rate of the signal obtained through the second reading process during the remaining half rotation period of the disk DK, the sector number Sopt2a and the second appropriate reading bias correction amount Xcopt2a when the bit error rate becomes the minimum can be obtained.

[0286] In this modification example 8, the same effects as those of the above modification example 3 and the above modification example 6 can also be obtained. In addition, the period of performing the second reading process may also include a second constant speed period in which the reading head RHD performs a seek at a constant speed between the second acceleration period PA2 and the second deceleration period PD2.

[0287] (Second Embodiment)

[0288] Next, the configuration of the disk device 1 according to the second embodiment will be described. Figure 30 These are diagrams showing the changes in the bit error rate ER, the changes in the read bias correction amount Xc, and the changes in the sector number of the target position when the read process, the seek operation, and the standby operation are repeatedly performed on the target track TR in the disk device 1 of the second embodiment. These are diagrams showing an example in which the bit error rate ER is roughly measured in the first range and then precisely measured in the second range smaller than the first range. Except for the configuration described in the second embodiment, the disk device 1 is configured in the same manner as the disk device 1 of the first embodiment.

[0289] As Figure 30 shown, similar to the first embodiment above ( Figure 17 ), the read processing unit 61b performs the first read process in the first range. In the first read process, the read processing unit 61b first sets the read bias correction amount Xc[i] to Xcs (Xc[0]) and reads the data of the sector SC0, and finally sets the read bias correction amount Xc[i] to Xce (Xc[k - 1]) and reads the data of the sector SCNs - 1. The first range is a range in the radial direction d1, a range to which all n1 radial positions PXr belong, and a range from the radial position PXrs to the radial position PXre.

[0290] Based on the distribution of the bit error rate of the signal obtained by reading the data of the track TR for one round, the Sopt1 as the sector number S when the bit error rate becomes the minimum and the first appropriate read bias correction amount Xcopt1 as the read bias correction amount Xc can be obtained, and the first appropriate read position PXropt1 can also be obtained.

[0291] In addition, the first appropriate read bias correction amount Xcopt1 obtained in the first read process is a coarse adjustment value, and the first appropriate read position PXropt1 is a coarse adjustment position. Therefore, as in the second embodiment, while satisfying the prerequisite of quickly finding an appropriate read position, an appropriate read bias correction amount Xcopt as a fine adjustment value more appropriate than the first appropriate read bias correction amount Xcopt1 and an appropriate read position PXropt as a fine adjustment position more appropriate than the first appropriate read position PXropt1 can be further derived.

[0292] Therefore, after the first read process, the read processing unit 61b repeatedly executes a set of operations multiple times as follows: sequentially performing a seek operation, a rotational waiting operation, and a third read process. The read processing unit 61b performs the third read process within the second range. The second range is a range that belongs to the first appropriate read position PXropt1 and is smaller than the first range in the radial direction d1, and is a range that belongs to n3 radial positions PXr that are offset from each other in the radial direction d1.

[0293] In the present second embodiment, the second range includes both sides of the first appropriate read position PXropt1. The n3 radial positions PXr of the second range include one or more radial positions PXr located on the outer circumference OD side of the first appropriate read position PXropt1 and one or more radial positions PXr located on the inner circumference ID side of the first appropriate read position PXropt1.

[0294] In addition, in the present second embodiment, the n3 radial positions PXr are selected from the n1 radial positions PXr. However, the n3 radial positions PXr may not be selected from the n1 radial positions PXr. In this case, for example, in the radial direction d1, the interval between the n3 radial positions PXr may be narrower than the interval between the n1 radial positions PXr.

[0295] In each of the above sets of operations, the read processing unit 61b performs a seek operation to move the read head RHD to one of the n3 radial positions PXr, performs a rotational waiting operation while maintaining the state where the read head RHD faces the one radial position PXr, and performs a third read process of reading the data of the track TR multiple times at the one radial position PXr.

[0296] The signal quality averaging processing unit 65 can derive a plurality of averaged qualities. Each averaged quality is a quality obtained by averaging the qualities of a plurality of third signals obtained by repeatedly reading at a corresponding one of the n3 radial positions PXr through the third read process.

[0297] The comparison unit 62 can also compare the plurality of averaged qualities and derive the averaged quality with the highest quality from the plurality of averaged qualities.

[0298] The determination unit 63 can also determine the radial position PXr at which the averaged quality with the highest quality is derived among the n3 radial positions PXr as the third appropriate read position PXropt3 that is more suitable for reading the data of the track TR than the first appropriate read position PXropt1.

[0299] Accordingly, when reading the data of the track TR, the read processing unit 61b can move the read head RHD to the third appropriate read position PXropt3, and read the data of the track TR at the third appropriate read position PXropt3.

[0300] Figure 31 It is a flowchart for explaining a method of finding the third appropriate read bias correction amount Xcopt3 applicable to the disk device 1 of the second embodiment. Figure 32 It is following Figure 31 and is a flowchart for explaining the above method. Figure 33 It is following Figure 32 and is a flowchart for explaining the above method.

[0301] As Figure 31 shown, when starting the method of finding the third appropriate read bias correction amount Xcopt3 for the track TR, first, in step STb1, the read processing unit 61b initializes the sector number S of the target position to 0 (S = 0).

[0302] Next, in step STb2, the read processing unit 61b moves the read head RHD to the radius position PXr(S) within the first range and positions it. Then, in step STb3, the read channel 14R measures the bit error rate ER(S).

[0303] The radius position PXr(S) is a position that is away from the reference position by a distance Xr(S) (Xr(S) = Xw + Xs + Xc(S)). The first range is a range having a width in the radial direction d1 and is a range from the radius position PXrs to the radius position PXre.

[0304] Then, in step STb4, the read processing unit 61b increments the sector number S of the target position. Next, in step STb5, the read processing unit 61b determines whether the sector number S of the target position has exceeded the final sector number Ns - 1. If the sector number S has not exceeded the sector number Ns - 1 (S ≤ Ns - 1), it moves to step STb2 and repeatedly executes the processing of steps STb2 to STb5.

[0305] On the other hand, when it is determined in step STb5 that the sector number S of the target position has exceeded the sector number Ns - 1 (S = Ns), the measurement of the bit error rate ER within the first range ends, and it moves to step STb6. In step STb6, the comparison unit 62 compares the bit error rates ER of the multiple first signals read by the first read processing, and derives the first signal with the minimum (preferably extremely small) bit error rate ER from the multiple first signals. Then, it is possible to find the sector number S, i.e., Smin, when the first signal with the minimum bit error rate ER is derived.

[0306] Next, in step STb7 , the determination unit 63 determines that the read offset correction amount Xc[Smin] when reading the sector SCmin having the sector number S of Smin is the first appropriate read offset correction amount Xcopt1 (Xcopt1 = Xc[Smin]).

[0307] like Figure 32 As shown, then, in step STb8, the reading processing unit 61b sets a second range that is smaller than the first range. The second range includes a radius position PXropt1 that is the first appropriate reading position PXropt1. The radius position PXropt1 is a position that is moved from the reference position by (Xw+Xs+Xcopt1). The reading bias correction amount Xc when the third reading process is performed within the second range is Xc[v]. For example, the reading processing unit 61b can use the following formula 3 to set the reading bias correction amounts Xc[0], Xc[1], Xc[2], Xc[3], and Xc[4] (n3=5) at the five radius positions PXr.

[0308] Xc[v]=Xcopt1+(v-2)×ΔQ…Equation 3

[0309] Here, the step size (in Japanese: step width) of reading the offset correction amount Xc is set to ΔQ.

[0310] Then, in step STb9 , the read processing unit 61 b ​​initializes the index v to 0 (v=0).

[0311] Next, in step STb10, the read processing unit 61b moves the read head RHD to the radial position PXr[v] within the second range and positions it. Next, in step STb11, the read channel 14R measures multiple bit error rates ER[v] of one track TR1 at the radial position PXr[v], and the signal quality averaging processing unit 65 derives the average value of the multiple bit error rates ER[v].

[0312] Then, in step STb12, the read processing unit 61b increments the index v. Next, in step STb13, the read processing unit 61b determines whether the index v exceeds the set value of 5. When the index v does not exceed 5 (v<5), the process proceeds to step STb10, and the processes of steps STb10 to STb13 are repeatedly performed.

[0313] On the other hand, in step STb13, when it is determined that the index v exceeds 5 (set value) (v = 5), the measurement of the bit error rate ER in the second range ends, and the process proceeds to step STb14. In step STb14, the comparison unit 62 compares the multiple average values read through the third read process, and derives the average value with the minimum (preferably extremely small) bit error rate ER from the multiple average values. Then, the index v, i.e., vmin, when the minimum average value is derived can be found.

[0314] Then, the determination unit 63 can determine the read bias correction amount Xc[vmin] when the index v is set to vmin as the third appropriate read bias correction amount Xcopt3. Thus, the method for finding the third appropriate read bias correction amount Xcopt3 for the track TR ends.

[0315] According to the disk device 1 of the second embodiment configured as described above and the method for finding the third appropriate read position PXropt3, the second embodiment can achieve the same effect as the first embodiment described above. After roughly measuring the large first range to derive the first appropriate read position PXropt1 (the first appropriate read bias correction amount Xcopt1), it is possible to narrow down to a smaller second range for precise measurement to derive the third appropriate read position PXropt3 (the third appropriate read bias correction amount Xcopt3).

[0316] 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 new 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 their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalents. It is also possible to combine two or more of the multiple embodiments and multiple modification examples as needed.

Claims

1. A magnetic disk device comprising: a disk having tracks on a recording layer; a read head that reads data from the recording layer of the disk; and A control unit having: a reading processing unit for executing a first reading processing, wherein the first reading processing is a processing for moving the reading head to n1 radial positions that are offset from each other in the radial direction of the disk during the period when the disk rotates m1 times, and reading data of the track at each of the radial positions; a comparing unit that compares the qualities of a plurality of first signals read out by the first reading process and derives a first signal of the highest quality from among the plurality of first signals; as well as a determination unit that determines the radial position at which the first signal of the highest quality is derived from among the n1 radial positions as a first appropriate reading position suitable for reading data of the track, Among them, 1≤m1<n1.

2. The magnetic disk device according to claim 1, When reading the data of the magnetic track, the read processing unit moves the read head to the first appropriate read position, and reads the data of the magnetic track at the first appropriate read position.

3. The magnetic disk device according to claim 1, The device further includes a reading channel configured to measure the quality of the plurality of first signals read out by the first reading process.

4. The magnetic disk device according to claim 1, The qualities of the plurality of first signals are amplitudes of the plurality of first signals, The first signal of the highest quality is a signal having the largest amplitude among the plurality of first signals.

5. The magnetic disk device according to claim 4, The first signal of the highest quality is a signal having a maximum amplitude among the plurality of first signals.

6. The magnetic disk device according to claim 1, The quality of the plurality of first signals is a bit error rate of the plurality of first signals, The first signal of the highest quality is a signal having the lowest bit error rate among the plurality of first signals.

7. The magnetic disk device according to claim 6, The first signal of the highest quality is a signal having a very low bit error rate among the plurality of first signals.

8. The magnetic disk device according to claim 1, When executing the first reading process, The reading processing unit causes the reading head to seek at a constant speed in a first seeking direction.

9. The magnetic disk device according to claim 8, The n1 radial positions are arranged at equal intervals in the radial direction, When executing the first reading process, The read processing unit reads data of the track at a constant time interval.

10. The magnetic disk device according to claim 8, The read processing unit sequentially performs a seek operation, a rotation waiting operation, and a second read processing after the first read processing. The second reading process is the following process: during the period when the disk rotates m2 times, the reading head is made to seek in the first seek direction, the reading head is moved to n2 radial positions that are offset from each other in the radial direction, and the data of the track is read at each of the radial positions. in, 1≤m2<n2, The operation of causing the pickup head to seek during the second reading process is the same as the operation of causing the pickup head to seek during the first reading process. A position where data of the track is first read in the first reading process and a position where data of the track is first read in the second reading process are offset from each other in the circumferential direction of the disk.

11. The magnetic disk device according to claim 8, The read processing unit performs a second read processing after the first read processing. The second reading process is the following process: during the period when the disk rotates m2 times, the reading head is made to seek at a constant speed in a second seek direction opposite to the first seek direction, the reading head is moved to n2 radial positions that are offset from each other in the radial direction, and the data of the track is read at each of the radial positions. in, 1≤m2<n2.

12. The magnetic disk device according to claim 11, The radial position at which the data of the track is read last in the first reading process is the same as the radial position at which the data of the track is read first in the second reading process. The radial position at which the data of the track is first read in the first reading process is the same as the radial position at which the data of the track is last read in the second reading process.

13. The magnetic disk device according to claim 1, The period for executing the first reading process includes a first acceleration period as a start period and a first deceleration period as a final period. The reading processing unit, During the first acceleration period, the pickup head is tracked in a first track seeking direction at a gradually increasing speed. During the first deceleration period, the pickup head is sought in the first seek direction at a gradually reduced speed.

14. The magnetic disk device according to claim 13, The n1 radial positions are arranged at equal intervals in the radial direction, The reading processing unit, During the first acceleration period, the data of the track is read at gradually shorter time intervals. During the first deceleration period, the data of the track is read with the time interval gradually lengthened.

15. The magnetic disk device according to claim 13, The read processing unit sequentially performs a seek operation, a rotation waiting operation, and a second read processing after the first read processing. The second reading process is the following process: during the period when the disk rotates m2 times, the reading head is made to seek in the first seek direction, the reading head is moved to n2 radial positions that are offset from each other in the radial direction, and the data of the track is read at each of the radial positions. in, 1≤m2<n2, The operation of causing the pickup head to seek during the second reading process is the same as the operation of causing the pickup head to seek during the first reading process. A position where data of the track is first read in the first reading process and a position where data of the track is first read in the second reading process are offset from each other in the circumferential direction of the disk.

16. The magnetic disk device according to claim 13, The read processing unit performs a second read processing after the first read processing. The second reading process is the following process: during the period when the disk rotates m2 times, the reading head is made to seek in a second seek direction opposite to the first seek direction, the reading head is moved to n2 radial positions that are offset from each other in the radial direction, and the data of the track is read at each of the radial positions. in, 1≤m2<n2, The period for executing the second reading process includes a second acceleration period as a start period and a second deceleration period as a final period. The reading processing unit, During the second acceleration, the pickup head is caused to seek in the second seek direction at a gradually increasing speed. During the second deceleration period, the pickup head is sought in the second seek direction at a gradually reduced speed.

17. The magnetic disk device according to any one of claims 10, 11, 15 and 16, The control unit further includes a reading position averaging processing unit, The comparison unit further compares the qualities of the plurality of second signals read out by the second reading process, and derives the second signal with the highest quality from the plurality of second signals. The determination unit further determines the radial position at which the second signal of the highest quality is derived from among the n2 radial positions as a second appropriate reading position suitable for reading data of the track, The reading position averaging processing unit derives an averaged position obtained by averaging the first appropriate reading position and the second appropriate reading position in the radial direction. When reading the data of the track, the read processing unit moves the read head to the averaging position and reads the data of the track at the averaging position.

18. The magnetic disk device according to claim 1, The control unit further includes a signal quality averaging processing unit. When the range in the radial direction to which all the n1 radial positions belong is set as the first range, and the range to which the first appropriate reading position belongs and to which n3 radial positions that are smaller than the first range in the radial direction and deviate from each other in the radial direction belong is set as the second range, After the first reading process, the reading processing unit repeatedly executes the following work groups a plurality of times: performing a seek operation, a rotation waiting operation, and a third reading process in sequence, In each of the working groups, the reading processing unit, The seek action is performed in order to move the pickup head to one of the n3 radial positions, The rotation waiting action is performed while maintaining the state where the reading head is facing the one radial position, executing the third reading process of reading the data of the track at the one radial position a plurality of times, The signal quality averaging processing unit derives a plurality of average qualities. Each of the averaged masses is a mass obtained by averaging the masses of a plurality of third signals read a plurality of times by the third reading process at a corresponding one of the n3 radial positions. The comparison unit further compares the plurality of average qualities and derives the highest average quality from the plurality of average qualities. The determination unit further determines the radial position at which the average quality of the highest quality is derived among the n3 radial positions as a third appropriate reading position more suitable for reading the data of the track than the first appropriate reading position. When reading the data of the magnetic track, the read processing unit moves the read head to the third appropriate read position, and reads the data of the magnetic track at the third appropriate read position.

19. The magnetic disk device according to claim 18, The n3 radial positions of the second range include: one or more radial positions located on the outer peripheral side of the first appropriate reading position; and One or more radial positions located on the inner peripheral side of the first appropriate reading position.

20. The magnetic disk device according to claim 1, further comprising: a write head that writes data to the recording layer of the disk; and an arm that supports the read head and the write head, The control unit further includes a write processing unit that executes a write process, wherein the write process is a process of moving the read head to a standby position and writing data to the track. When the first appropriate reading position is a position offset from the standby position and the data of the track is to be read, the reading processing unit moves the reading head to the first appropriate reading position offset from the standby position and reads the data of the track at the first appropriate reading position. When the first appropriate reading position coincides with the standby position and the data of the track is read, the reading processing unit moves the reading head to the first appropriate reading position as the standby position and reads the data of the track at the first appropriate reading position.

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