Magnetic disk device

Abstract

To provide a magnetic disk device capable of suppressing errors between a target track and a position of a magnetic head during a write operation.SOLUTION: A controller of a magnetic disk device operates as follows in a first operation of writing a data area by positioning a magnetic head. That is, the controller acquires a first burst demodulate value by demodulating a burst pattern and corrects the first burst modulate value based on a correction algorithm using a first set value as an argument. Then, the controller calculates the offset amount from a servo track of the magnetic head from one of a plurality of servo tracks based on the corrected first burst demodulated value.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present embodiment relates to a magnetic disk device. [Background technology]

[0002] Conventionally, a magnetic disk drive positions a magnetic head based on servo data recorded on a magnetic disk. The magnetic disk has a plurality of tracks. In a write operation or a read operation, the magnetic disk drive positions the magnetic head on a target track. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Pat. No. 9,564,157 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment is to provide a magnetic disk drive capable of suppressing an error between a target track and a magnetic head position during a write operation. [Means for solving the problem]

[0005] According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head, a memory, and a controller. The magnetic disk includes a plurality of servo tracks, and a plurality of servo sectors, each of which records servo data including a burst pattern, are arranged at intervals in the circumferential direction on the plurality of servo tracks. A data area, in which data is written, is arranged between the servo sectors arranged in the circumferential direction. The magnetic head performs writing and reading on the magnetic disk. A first setting value is stored in the memory. In a first operation in which data is written to the data area while positioning the magnetic head, the controller operates as follows. That is, the controller demodulates the burst pattern to obtain a first burst demodulation value, and corrects the first burst demodulation value based on a correction algorithm that uses the first setting value as an argument. Then, the controller calculates an offset amount of the magnetic head from one of the plurality of servo tracks based on a second burst demodulation value, which is the corrected first burst demodulation value. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a magnetic disk device according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing an example of the configuration of a magnetic disk according to the embodiment. [Diagram 3] FIG. 3 is a diagram illustrating an example of servo data recorded in a servo sector according to the embodiment. [Figure 4] FIG. 4 is a schematic diagram showing an example of the configuration of an N burst and a Q burst recorded in a servo sector of the embodiment. [Diagram 5] FIG. 5 is a diagram for explaining an example of a method for learning the RRO correction amount. [Figure 6] FIG. 6 is a diagram showing an example of a position error observed during a write operation and during a non-write operation. [Figure 7] FIG. 7 is a schematic diagram illustrating an example of a functional configuration related to positioning control of the magnetic disk device according to the embodiment. [Figure 8] FIG. 8 is a flowchart illustrating an example of an operation for generating correction setting information according to the embodiment. [Figure 9] FIG. 9 is a flowchart showing an example of a positioning operation during a non-write operation. [Figure 10] FIG. 10 is a flowchart showing an example of a positioning operation during a write operation. [Figure 11] FIG. 11 is a diagram showing an example of the amplitude of the demodulated signal of the N burst and the amplitude of the demodulated signal of the Q burst in a burst demodulation value set during a non-write operation. [Figure 12] FIG. 12 is a diagram showing an example of the phase of the demodulated signal of the N burst and the phase of the demodulated signal of the Q burst in a burst demodulated value set during a non-write operation. [Figure 13] FIG. 13 is a diagram showing an example of the amplitude of the demodulated signal of the N burst and the amplitude of the demodulated signal of the Q burst in a burst demodulation value set during a write operation. [Figure 14] FIG. 14 is a diagram showing an example of the phase of the demodulated signal of the N burst and the phase of the demodulated signal of the Q burst in a burst demodulated value set during a write operation. [Figure 15] Figure 15 is a graph plotting on a two-dimensional plane burst data after initial phase correction calculated from a burst demodulation value set during a non-write operation, and burst data after initial phase correction calculated from a burst demodulation value set during a write operation without correction using correction setting information. [Figure 16] FIG. 16 is a diagram showing an example of the amplitude ratio in the correction setting information. [Figure 17] FIG. 17 is a diagram showing an example of the phase difference in the correction setting information. [Figure 18] Figure 18 is a diagram showing an example of the difference between the second servo demodulation position calculated from a burst demodulation value set during a non-write operation and the second servo demodulation position calculated without correction using correction setting information from a burst demodulation value set during a write operation, observed at multiple servo sectors SV on a servo track. [Figure 19]Figure 19 is a diagram showing an example of the difference between the second servo demodulation position calculated from the burst demodulation value set during a non-write operation and the second servo demodulation position calculated by performing correction using correction setting information from the burst demodulation value set during a write operation, observed at multiple servo sectors SV on a servo track. [Figure 20] Figure 20 is a diagram showing an example of the difference between the second servo demodulation position calculated from a burst demodulation value set during a non-write operation and the second servo demodulation position calculated by correcting only the amplitude from a burst demodulation value set during a write operation, observed at multiple servo sectors SV on a servo track. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] A magnetic disk device according to an embodiment will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to the embodiment.

[0008] (Embodiment) FIG. 1 is a schematic diagram showing an example of the configuration of a magnetic disk device 1 according to an embodiment.

[0009] The magnetic disk device 1 is connected to a host 2. The magnetic disk device 1 can receive access commands, such as a write command and a read command, from the host 2.

[0010] The magnetic disk device 1 includes a magnetic disk 11 having a magnetic layer formed on its surface. The magnetic disk device 1 accesses the magnetic disk 11 in response to an access command. The access includes writing data and reading data.

[0011] Data is written and read by a magnetic head 22. Specifically, in addition to a magnetic disk 11, the magnetic disk device 1 includes a spindle motor (SPM) 12, a ramp 13, an actuator arm 15, a voice coil motor (VCM) 16, a servo controller (SVC) 21, a magnetic head 22, a hard disk controller (HDC) 23, a preamplifier 24, a read / write channel (RWC) 25, a processor 26, a flash read only memory (FROM) 28, and a dynamic random access memory (DRAM) 29.

[0012] The magnetic disk 11 is rotated at a predetermined rotational speed by the SPM 12 attached coaxially.

[0013] The SVC 21 is an integrated circuit that functions as a driver for driving the SPM 12 and the VCM 16. The processor 26 controls the rotation of the SPM 12 and the VCM 16 via the SVC 21.

[0014] The magnetic head 22 writes and reads data to and from the magnetic disk 11 using a write head 22w and a read head 22r provided thereto. The magnetic head 22 is attached to the tip of an actuator arm 15. The magnetic head 22 is moved in the radial direction of the magnetic disk 11 by a VCM 16 driven by an SVC 21. Note that a plurality of either one or both of the write head 22w and the read head 22r provided to the magnetic head 22 may be provided for a single magnetic head 22.

[0015] When the magnetic disk 11 is not rotating, the magnetic head 22 is moved onto the ramp 13. The ramp 13 is configured to hold the magnetic head 22 at a position separated from the magnetic disk 11.

[0016] The preamplifier 24 is an integrated circuit that writes and reads data via the magnetic head 22. During a read operation, the preamplifier 24 amplifies and outputs a signal read by the magnetic head 22 from the magnetic disk 11, and supplies the signal to the RWC 25. During a write operation, the preamplifier 24 amplifies a signal corresponding to the data to be written, which is supplied from the RWC 25, and supplies the signal to the magnetic head 22.

[0017] The HDC 23 controls data transmission and reception between the host 2 via the I / F bus, and controls the DRAM 29 .

[0018] The DRAM 29 is used as a buffer for data transmitted to and received from the host 2. For example, the DRAM 29 is used to temporarily store data to be written or data read from the magnetic disk 11.

[0019] Furthermore, the DRAM 29 is used as an operating memory by the processor 26. The DRAM 29 is used as an area into which firmware programs are loaded and an area in which various types of management data are temporarily stored.

[0020] The RWC 25 modulates the data to be written that is supplied from the HDC 23 and supplies the modulated data to the preamplifier 24. The RWC 25 also performs demodulation, including error correction, on the signal that is read from the magnetic disk 11 and supplied from the preamplifier 24, and then outputs the signal to the HDC 23 as digital data.

[0021] The processor 26 is, for example, a CPU (Central Processing Unit). A FROM (Flash Read Only Memory) 28 and a DRAM 29 are connected to the processor 26.

[0022] Firmware programs and various setting information are stored in the FROM 28. The firmware programs may be stored in the magnetic disk 11.

[0023] The processor 26 performs overall control of the magnetic disk device 1 in accordance with a firmware program stored in the FROM 28 or the magnetic disk 11. For example, the processor 26 loads the firmware program from the FROM 28 or the magnetic disk 11 into the DRAM 29, and controls the SVC 21, the preamplifier 24, the RWC 25, the HDC 23, and the like in accordance with the firmware program loaded into the DRAM 29.

[0024] It should be noted that some or all of the functions of the processor 26 may be realized by a hardware circuit such as a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

[0025] The HDC 23, the RWC 25, and the processor 26 are configured as a single integrated circuit, a System-On-a-Chip (SoC) 30. The SoC 30 may include other elements (such as a ROM 28 or a DRAM 29) in addition to the above. The SoC 30 is an example of a controller.

[0026] 2 is a schematic diagram showing an example of the configuration of the magnetic disk 11 according to the embodiment. Note that this diagram shows an example of the rotation direction of the magnetic disk 11. The magnetic head 22 moves relatively to the magnetic disk 11 as the magnetic disk 11 rotates. Therefore, the write / read direction, i.e., the direction in which data is written or read by the magnetic head 22 along the circumferential direction, is opposite to the rotation direction of the magnetic disk 11.

[0027] In the radial direction, the direction from the edge to the center of the magnetic disk 11 is the inner diameter (ID) direction, and the direction from the center to the edge of the magnetic disk 11 is the outer diameter (OD) direction.

[0028] In the manufacturing process, servo data used for positioning the magnetic head 22 is written on the magnetic disk 11, for example, by a servo writer or by self-servo writing (SSW). As shown in Fig. 2, as an example of the arrangement of servo areas in which servo data is written, a plurality of servo areas SV are formed arranged radially in the radial direction and at a predetermined interval in the circumferential direction. A data area DA in which data is written is arranged between two consecutive servo areas SV in the circumferential direction.

[0029] A plurality of concentric servo tracks 41 are provided in the radial direction of the magnetic disk 11. The servo data written in the servo areas SV is used to control the positioning of the magnetic head 22.

[0030] More specifically, a plurality of concentric data tracks are provided on an area of ​​the magnetic disk 11 where the plurality of servo tracks 41 are provided. The plurality of servo tracks 41 may be used as a plurality of data tracks, or a plurality of data tracks different from the plurality of servo tracks 41 may be provided. A plurality of data sectors are arranged in a circumferential direction in an area divided by the data areas DA on each data track. Data can be written to each data sector by the magnetic head 22. The data that can be written to each data sector includes user data received from the host 2, metadata (e.g., error correction code) associated with the user data, system data, and the like. The magnetic disk device 1 holds in advance settings of the positional relationship between the plurality of servo tracks 41 and the plurality of data tracks. The magnetic disk device 1 executes positioning control for positioning the magnetic head 22 on a target data track based on the servo data recorded in the servo area SV. The positioning control includes a seek operation for moving the magnetic head 22 in a radial direction toward the target data track, a tracking operation for maintaining the magnetic head 22 on the target data track, and the like.

[0031] An area divided by the servo areas SV on the servo track 41 is referred to as a servo sector SV. That is, on the servo tracks 41, a plurality of servo sectors SV are arranged at intervals in the circumferential direction.

[0032] 3 is a diagram showing an example of servo data recorded in a servo sector SV according to an embodiment. In this example, in the radial direction, one servo sector SV has a width equivalent to approximately three data tracks. This diagram shows the configuration of a servo sector SV that spans three data tracks #M-1, #M, and #M+1.

[0033] As shown in FIG. 3, in the servo sector SV, a preamble, a servo mark, a gray code, an N burst, a Q burst, and a post code are recorded in this order in the write / read direction.

[0034] The preamble is a single periodic pattern data that changes periodically in the circumferential direction. The preamble is used to adjust the amplitude, phase and frequency of the sampling data when the servo waveform read by the read head 22r is input to the RWC 25 as sampling data based on the servo clock.

[0035] The servo marks are pattern data for determining the demodulation timing of the servo data. Based on the detection timing of the servo marks, the controller 30 determines the demodulation timing of various servo data subsequently read by the read head 22r.

[0036] The gray code includes a cylinder address for identifying each servo track 41 provided on the magnetic disk 11 and a sector address for identifying each servo sector SV on the servo track 41 .

[0037] The N burst and the Q burst are pattern data used to detect the amount of positional deviation from the track center of the servo track 41 indicated by the cylinder address included in the Gray code. The amount of positional deviation from the track center of the servo track 41 is expressed as a burst offset.

[0038] 4 is a schematic diagram showing an example of the configuration of the N burst and the Q burst recorded in the servo sector SV of the embodiment. In this figure, the dot-hatched pattern indicates one of two values ​​with different polarities (e.g., magnetization with a positive polarity), and the white pattern indicates the other of the two values ​​(e.g., magnetization with a negative polarity).

[0039] The length in the radial direction may be expressed in servo track units, in other words, units of spatial length assuming the servo track pitch to be 1. The unit of spatial length assuming the servo track pitch to be 1 is denoted as Svtrk.

[0040] In the example shown in Fig. 4, the N burst and the Q burst each have a configuration in which the polarity is reversed at a predetermined length interval in the circumferential direction. In the radial direction, the polarity of each of the N burst and the Q burst is reversed every 1 Svtrk. The N burst is recorded so that the maximum amplitude is obtained at a position offset by 0.5 Svtrk from the track center. The Q burst is recorded so that the maximum amplitude is obtained at the track center.

[0041] The RWC25 captures the burst pattern (i.e., each of the N burst and the Q burst) at a sampling interval based on the servo clock. The RWC25 performs, for example, a Discrete Fourier Transform (DFT) process on the burst sampling waveform obtained thereby to obtain the sine component and cosine component of the burst frequency, or the phase and amplitude. As an example, the RWC25 is described as obtaining the phase and amplitude. In the following, the phase and amplitude of the burst frequency obtained by performing the DFT process on the burst sampling waveform may be referred to as the phase and amplitude of the demodulated signal of the burst pattern.

[0042] The SoC 30 (e.g., the processor 26) calculates a burst offset based on the phase and amplitude of the demodulated signal of the burst pattern. The burst offset is an offset amount from one servo track 41. The SoC 30 calculates the radial position of the magnetic head 22 based on the cylinder address and the burst offset.

[0043] Let us return to the explanation of Figure 3. The ideal shape of the tracks (data tracks and servo tracks 41) is a perfect circle. However, the servo tracks 41 are distorted due to vibrations received when writing servo data, servo pattern quality, and other factors. Therefore, the radial position (radial position) of the servo track 41 specified based on a combination of the cylinder address and burst offset may deviate from the radial position of the servo track 41 with an ideal shape. This position deviation occurs repeatedly in the same way with one rotation of the magnetic disk 11 (and SPM 12) as a period, and is therefore called RRO (Repeatable RunOut). The postcode is a coded version of the correction amount for this RRO.

[0044] The SoC 30 (e.g., the processor 26) obtains the radial position of the magnetic head 22 obtained by combining the cylinder address and the burst offset by performing a correction using the RRO correction amount recorded as the postcode, thereby obtaining the radial position of the magnetic head 22 with the position shift caused by the RRO canceled. The correction using the RRO correction amount is referred to as the RRO correction.

[0045] FIG. 5 is a diagram for explaining an example of a method for learning the RRO correction amount.

[0046] In the manufacturing process of the magnetic disk device 1, after the gray code and burst pattern are written, learning of the RRO compensation amount is performed. In the process of learning the RRO compensation amount, a plurality of servo tracks 41 or data tracks are set as target tracks in sequence, and for each target track, the difference between the actual radial position of the magnetic head 22 and the radial position of the target track is measured under positioning control based on the gray code and burst pattern.

[0047] That is, the SoC 30 reads the gray code and burst pattern by the read head 22r, and estimates the position of the magnetic head 22 based on the read gray code and burst pattern. Then, the SoC 30 positions the magnetic head 22 on the target track based on the estimated position of the magnetic head 22. During this time, the SoC 30 obtains the deviation amount of the estimated position of the magnetic head 22 from the target track as the RRO correction amount.

[0048] The dotted line in Fig. 5 is a trajectory of the magnetic head 22 observed under control of positioning on a target track in the process of learning the RRO correction amount. The SoC 30 acquires the position of the magnetic head 22, for example, every time the magnetic head 22 passes a servo sector SV. Therefore, the observed trajectory has a polygonal line shape as shown in this figure. The SoC 30 acquires the radial deviation of the position of the magnetic head 22 in each servo sector SV from the target track as the RRO correction amount in each servo sector SV. The SoC 30 records each RRO correction amount as a postcode in the corresponding servo sector SV.

[0049] 5 is merely an example, and the method of calculating the RRO correction amount in each servo sector SV from the observed trajectory can be modified in various ways.

[0050] Hereinafter, the phase and amplitude of the demodulated signal of the burst pattern obtained by demodulating the burst pattern will be referred to as a burst demodulation value set. The burst demodulation value set includes the phase and amplitude of the demodulated signal of the N burst and the phase and amplitude of the demodulated signal of the Q burst.

[0051] The estimated position of the magnetic head 22 obtained by adding the cylinder address and the burst offset is referred to as a first servo demodulation position. The first servo demodulation position after RRO correction, which is the estimated position of the magnetic head 22 finally used for positioning, is referred to as a second servo demodulation position.

[0052] One example of a method for increasing the storage capacity of a magnetic disk drive is to make the radial interval between data tracks, that is, the track pitch of the data tracks, as small as possible. If the position error between the magnetic head and the target track (hereinafter, the position error does not include NRPE: Non Repeatable Position Error, but is explained as a position error RPE (Repeatable Position Error) synchronized with rotation) can be minimized by controlling the position of the magnetic head so that the magnetic head does not follow the RRO, the track pitch of the data tracks can be reduced to increase the storage capacity of the magnetic disk drive. If the RRO can be completely corrected, the error RPE between the position of the magnetic head and the target track can be made zero. As a result, it is possible to set multiple data tracks at equal intervals in the radial direction without the need to provide a margin for compensating for data that takes the position error RPE into account, and it is possible to make the capacity loss due to the position error RPE zero.

[0053] Here, the observed position error RPE may differ depending on whether a write operation is in progress or a non-write operation is in progress.

[0054] A write operation is an operation for writing data to a data sector while positioning the magnetic head 22. That is, in a write operation, when the magnetic head 22 passes a servo sector SV, the servo sector SV is read, and when the magnetic head 22 passes a certain data sector, data is written to the data sector.

[0055] A non-write operation is an operation that positions the magnetic head 22 but does not write data to a data sector. Various operations fall under the category of non-write operations.

[0056] For example, a read operation for reading data from a data sector corresponds to a non-write operation. In a read operation, when the magnetic head 22 passes a servo sector SV, the servo sector SV is read, and when the magnetic head 22 passes a target data sector, data is read from the target data sector.

[0057] Furthermore, when starting a write operation, the SoC 30 executes a seek operation to move the magnetic head 22 to a target data track, and positions the magnetic head 22 on the target data track. When the positioning of the magnetic head 22 on the target data track is completed and the magnetic head 22 reaches a position of the target data sector, the SoC 30 starts the write operation. A part or all of the operations that involve positioning before the start of a write operation correspond to non-write operations.

[0058] For example, DFH (Dynamic Flying Height) technology is known as a technology for enabling high-quality writing. According to DFH technology, the flying height of the magnetic head is adjustable. During a write operation, the flying height of the magnetic head is controlled to a predetermined small value. Specifically, control is started to set the flying height of the magnetic head to a predetermined small value prior to the start of a write operation, and then the write operation is started. The operation from when the flying height of the magnetic head is controlled to a predetermined small value until the start of a write operation corresponds to a non-write operation.

[0059] In addition, in the process of learning the RRO compensation amount described above, the operation of reading servo data from each servo sector SV does not write any data. That is, in the process of learning the RRO compensation amount described above, the operation of positioning the magnetic head 22 corresponds to a non-write operation.

[0060] 6 is a diagram showing an example of the position error RPE observed during a write operation and during a non-write operation. This diagram shows the position error RPE observed during each operation when the magnetic head 22 is positioned on data track #M among three data tracks (data track #M-1, data track #M, data track #M+1) aligned in the radial direction. As shown in this diagram, it can be seen that the position error RPE observed during a write operation is worse than the position error RPE observed during a non-write operation.

[0061] The reason why the position error RPE observed during a write operation is worse than the position error RPE observed during a non-write operation is as follows: That is, when the servo demodulation position calculated based on the burst demodulation value set during a write operation is corrected using the RRO correction amount calculated based on the burst demodulation value set during a non-write operation, the RRO correction value may not be appropriate. The reason why the RRO correction value becomes inappropriate is that the burst demodulation value set during a write operation may differ from the burst demodulation value set during a non-write operation. Since the servo demodulation position is the result of calculation based on a specific formula for a certain burst demodulation value set, if the burst demodulation value set changes, the servo demodulation position will change. In other words, the RRO will look different. The reason why the burst demodulation value set is different during write operation and non-write operation is because the transient response (floating height of the magnetic head, temperature, leakage magnetic field from the write head, and time for the read output to stabilize) when transitioning from a state in which data is written to a state in which servo data is read affects the reading of the burst waveform.

[0062] In the embodiment, during a write operation, the SoC 30 performs a correction on the burst demodulation value set obtained during the write operation to bring the burst demodulation value set obtained during the non-write operation closer to the burst demodulation value set obtained during the non-write operation, thereby suppressing the deterioration of the position error RPE during the write operation.

[0063] Hereinafter, the burst demodulation value set obtained by positioning control during a non-write operation may be referred to as the burst demodulation value set during a non-write operation, and the burst demodulation value set obtained by positioning control during a write operation may be referred to as the burst demodulation value set during a write operation.

[0064] FIG. 7 is a schematic diagram showing an example of a functional configuration related to positioning control of the magnetic disk device 1 according to the embodiment.

[0065] The RWC 25 includes a Gray code demodulation unit 251 and a burst demodulation unit 252. The processor 26 functions as a first correction unit 261, a second correction unit 262, a third correction unit 263, and a correction setting information generation unit 264 based on a firmware program.

[0066] The RWC 25 receives a servo waveform from the preamplifier 24 .

[0067] The Gray code demodulation unit 251 obtains a cylinder address by decoding the Gray code waveform included in the input servo waveform. The burst demodulation unit 252 obtains a burst demodulation value set by performing demodulation, i.e., DFT processing, on the burst waveform included in the input servo waveform.

[0068] During a write operation, the first correction unit 261 performs correction on the burst demodulation value set to bring it closer to the burst demodulation value set during a non-write operation, using the correction setting information 300 generated in advance. Then, the first correction unit 261 outputs the corrected burst demodulation value set to the second correction unit 262.

[0069] When a non-write operation is in progress, the first correction unit 261 outputs the burst demodulated value set to the second correction unit 262 without performing any correction on the burst demodulated value set.

[0070] The second correction unit 262 calculates a burst offset based on the input burst demodulation value set, and the burst offset is added to the cylinder address to obtain a first servo demodulation position.

[0071] The third correction unit 263 acquires a second servo demodulated position by executing correction based on the RRO correction amount for the first servo demodulated position, and outputs the second servo demodulated position.

[0072] The correction setting information generating unit 264 generates the correction setting information 300. The correction setting information 300 is numerical information used as an argument of a correction algorithm that brings a burst demodulation value set obtained during a write operation closer to a burst demodulation value set obtained during a non-write operation. The correction setting information 300 and the correction algorithm will be described in detail later.

[0073] The correction setting information 300 generated by the correction setting information generating unit 264 is stored in a predetermined memory. Here, the memory in which the correction setting information 300 is stored is assumed to be FROM 28 as an example. The memory in which the correction setting information 300 is stored is not limited to this. The correction setting information 300 may be stored in a system area provided on the magnetic disk 11, or in each servo sector SV. The correction setting information 300 may be stored in a non-volatile memory different from both the magnetic disk 11 and FROM 28. In addition, during operation, the correction setting information 300 may be loaded into the DRAM 29, and the processor 26 may use the correction setting information 300 loaded into the DRAM 29.

[0074] In the above description, the first correction unit 261, the second correction unit 262, the third correction unit 263, and the correction setting information generation unit 264 are implemented by the processor 26. Some or all of these functional components may be implemented by a hardware circuit such as an FPGA or an ASIC. Also, some or all of these functional components may be provided in an integrated circuit other than the processor 26, such as the RWC 25.

[0075] Next, the operation of the magnetic disk device 1 according to the embodiment and the processing of some of the functional components will be described in detail.

[0076] 8 is a flowchart showing an example of the operation of generating the correction setting information 300 of the embodiment. Here, an example is described in which the correction setting information 300 related to a certain servo sector SV (referred to as a target servo sector SV) is generated. Note that the series of processes shown in this figure are executed, for example, in the manufacturing process, after the learning and recording of the RRO are completed. Note that the execution timing of this series of processes is not limited to this. This series of processes may be executed after the magnetic disk device 1 is shipped.

[0077] First, the correction setting information generating unit 264 executes a non-write operation on the servo track 41 or data track including the target servo sector SV, and acquires a burst demodulation value set during the non-write operation related to the target servo sector SV (S101). Specifically, the correction setting information generating unit 264 demodulates the burst pattern while positioning the magnetic head 22 without writing to the data area DA, and acquires the burst demodulation value set obtained by demodulation as a burst demodulation value set during the non-write operation. Among the burst demodulation value sets during the non-write operation acquired by the process of S101, the amplitude of the demodulation signal of the N burst is represented as Namp0, the phase of the demodulation signal of the N burst is represented as Nphs0, the amplitude of the demodulation signal of the Q burst is represented as Namp0, and the phase of the demodulation signal of the Q burst is represented as Nphs0.

[0078] Next, the correction setting information generating unit 264 executes a write operation on the servo track 41 including the target servo sector SV or a data track, and acquires a burst demodulation value set during the write operation related to the target servo sector SV (S102). Specifically, the correction setting information generating unit 264 writes to the data area DA and demodulates the burst pattern at the position while positioning the magnetic head 22, and acquires the burst demodulation value set obtained by demodulation as a burst demodulation value set during the write operation. Of the burst demodulation value sets during the write operation acquired by the process of S102, the amplitude of the demodulation signal of the N burst is represented as Namp1, the phase of the demodulation signal of the N burst is represented as Nphs1, the amplitude of the demodulation signal of the Q burst is represented as Namp1, and the phase of the demodulation signal of the Q burst is represented as Nphs1.

[0079] Next, the correction setting information generating unit 264 calculates the correction setting information 300 for the target servo sector SV (S103). The generating unit 264 calculates the correction setting information 300 based on the following Equations 1 to 4.

[0080] Ngain=Namp0 / Namp1 (Equation 1) Qgain=Qamp0 / Qamp1 (Formula 2) Nphsofs = Nphs0 - Nphs1 (Equation 3) Qphsofs=Qphs0-Qphs1 (Equation 4)

[0081] In this example, the correction setting information 300 is a set consisting of an amplitude ratio Ngain of the demodulated signal of the N burst, an amplitude ratio Qgain of the demodulated signal of the Q burst, a phase difference Nphsofs of the demodulated signal of the N burst, and a phase difference Qphsofs of the demodulated signal of the Q burst.

[0082] Next, the correction setting information generating unit 264 stores the correction setting information 300 obtained by the calculation in the FROM 28 (S104). Then, the operation of generating the correction setting information 300 related to the target servo sector SV is completed.

[0083] 8 is executed for each of the servo sectors SV of the magnetic disk 11. In such a case, the correction setting information 300 is generated and stored for each servo sector SV.

[0084] One piece of correction setting information 300 is used for positioning in one corresponding servo sector SV. However, one piece of correction setting information 300 may be shared by multiple servo sectors SV.

[0085] For example, the correction setting information generating unit 264 averages the burst demodulation value set during non-write operation and the burst demodulation value set during write operation for a group of servo sectors SV, and calculates the correction setting information 300 based on the burst demodulation value set during non-write operation averaged for the group of servo sectors SV and the burst demodulation value set during write operation averaged for the group of servo sectors SV. Then, the first correction unit 261 uses the correction setting information 300 generated from the group of servo sectors SV in positioning in any servo sector SV among the group of servo sectors SV.

[0086] Alternatively, the correction setting information generating unit 264 executes the processes of S101 to S104 for each servo sector SV. Then, the correction setting information generating unit 264 averages the correction setting information 300 generated for each servo sector SV for a group of servo sector SVs. Then, the first correction unit 261 uses the correction setting information 300 averaged for the group of servo sector SVs for positioning in any servo sector SV in the group of servo sector SVs.

[0087] In this way, by sharing one correction setting information 300 among a group of servo sectors SV, it is possible to reduce the capacity required to store the correction setting information 300 and to reduce the time required to read the correction setting information 300 when positioning.

[0088] The method of determining the group of servo sectors SV that share one correction setting information 300 is arbitrary. One correction setting information 300 may be shared by all servo sectors SV included in one servo track 41 or data track. The recording surface of the magnetic disk 11 may be divided into a plurality of zones arranged in the radial direction, and one correction setting information 300 may be shared by all servo sectors SV included in each zone.

[0089] In other words, the correction setting information generation unit 264 may calculate one piece of correction setting information 300 for two or more servo sectors SV and store it in FROM 28, or may calculate one piece of correction setting information 300 for two or more servo tracks 41 or data tracks and store it in FROM 28.

[0090] 9 is a flow chart showing an example of the positioning operation during a non-write operation, in which the operation when the magnetic head 22 passes over a certain servo sector SV during a non-write operation will be described.

[0091] First, the Gray code demodulation unit 251 acquires a cylinder address (S201). Next, the burst demodulation unit 252 acquires a burst demodulation value set (S202). Of the acquired burst demodulation value set, the amplitude of the demodulated signal of the N burst is represented as Namp, the phase of the demodulated signal of the N burst is represented as Nphs, the amplitude of the demodulated signal of the Q burst is represented as Qamp, and the phase of the demodulated signal of the Q burst is represented as Qphs.

[0092] The first correction unit 261 outputs the burst demodulation value set acquired by the process of S202 to the second correction unit 262.

[0093] The second correction unit 262 calculates a burst offset based on the input burst demodulation value set, that is, the set of Namp, Nphs, Qamp, and Qphs (S203).

[0094] The second correction unit 262 may use any algorithm to calculate the burst offset based on the burst demodulation value set. An example of an algorithm to calculate the burst offset based on the burst demodulation value set will be described.

[0095] The second correction unit 262 calculates the burst offset BstPos1 by using the following Equations 5 to 10. Note that in this specification, "*" is an operator meaning multiplication. Nbst1=Namp*sin(Nphs+PhsCmp) (Formula 5) Qbst1=Qamp*sin(Qphs+PhsCmp) (Equation 6) Nbst2=cos(AzmCmp)*Nbst1-sin(AzmCmp)*Qbst1 (Equation 7) Qbst2=sin(AzmCmp)*Nbst1+cos(AzmCmp)×Qbst1 (Equation 8) BstPos0=arctan(Qbst2 / Nbst2) (Equation 9) BstPos1=BstPos0+TableCmp (Equation 10)

[0096] The process represented by Equation 5 and Equation 6 is called initial phase correction. PhsCmp is the correction value of the initial phase correction, that is, the initial phase correction value. The initial phase correction value is adjusted so that the amplitudes Namp and Qamp of the burst demodulation value set are maximized. Nbst1 and Qbst1 are the burst data after the initial phase correction.

[0097] The processing expressed by Equation 7 and Equation 8 is called rotation correction. AzmCmp is a value for correcting the burst data after the initial phase correction, and is a rotation correction value. Nbst2 and Qbst2 are the burst data after the rotation correction.

[0098] Equation 9 represents the process of calculating the phase angle represented by the points of the burst data Nbst2 and Qbst2 after rotation correction when the horizontal axis is the N burst data axis and the vertical axis is the Q burst data axis. Since a phase angle of 360 degrees corresponds to a distance of 2Svtrk, the phase obtained by equation 9 can be considered to represent the burst offset. The phase obtained by equation 9 is represented as the burst offset BstPos0. Note that a phase angle of ±180 degrees can be calculated as a burst offset of ±1Svtrk.

[0099] Equation 10 is a calculation for correcting a part of the deviation of the burst offset from the target track, and is called table correction. TableCmp is a table correction value adjusted for the burst offset BstPos0 obtained by the calculation of Equation 9. BstPos1 obtained by the calculation of Equation 10 is the burst offset after the table correction. The second correction unit 262 outputs the burst offset BstPos1.

[0100] In the processor 26, the burst offset BstPos1 is added to the cylinder address acquired by the Gray code demodulation unit 251. The third correction unit 263 executes RRO correction on the first servo demodulation position obtained by adding the burst offset BstPos1 and the cylinder address (S204). The second servo demodulation position is obtained by the RRO correction on the first servo demodulation position.

[0101] Processor 26 uses the second servo demodulation position as the current position of magnetic head 22 to perform positioning to bring magnetic head 22 closer to the target data track (S205). Then, the operation when magnetic head 22 passes a certain servo sector SV during a non-write operation ends. SoC 30 can position magnetic head 22 on the target data track by repeatedly executing the processes of S201 to S205 during a non-write operation.

[0102] 10 is a flow chart showing an example of the positioning operation during a write operation, which will be described below when the magnetic head 22 passes over a certain servo sector SV during a write operation.

[0103] First, the Gray code demodulation unit 251 acquires a cylinder address (S301). Next, the burst demodulation unit 252 acquires a burst demodulation value set (S302). Of the acquired burst demodulation value set, the amplitude of the demodulated signal of the N burst is represented as Nampw, the phase of the demodulated signal of the N burst as Nphsw, the amplitude of the demodulated signal of the Q burst as Qampw, and the phase of the demodulated signal of the Q burst as Qphsw.

[0104] The first correction unit 261 acquires correction setting information 300, that is, a set of Ngain, Qgain, Nphsofs, and Qphsofs (S303). Then, the first correction unit 261 corrects the burst demodulation value set, that is, a set of Nampw, Nphsw, Qampw, and Qphsw, using the correction setting information 300 as an argument of a correction algorithm (S304). The first correction unit 261 corrects the burst demodulation value set by using the correction algorithm shown in the following Equations 11 to 14.

[0105] Nampc=Ngain*Nampw (Eq. 11) Qampc=Qgain*Qampw (Equation 12) Nphsc=Nphsw+Nphsofs (Eq. 13) Qphsc=Qphsw+Qphsofs (Eq. 14)

[0106] Nampc is the amplitude Nampw of the demodulated signal of the N burst after correction. Qampc is the amplitude Qampw of the demodulated signal of the Q burst after correction. Nphsc is the phase Nphsw of the demodulated signal of the N burst after correction. Qphsc is the phase Qphsw of the demodulated signal of the Q burst after correction.

[0107] The first correction unit 261 outputs the corrected burst demodulation value set acquired by the process of S304 to the second correction unit 262.

[0108] The second correction unit 262 calculates a burst offset based on the input burst demodulation value set, i.e., the set of Nampc, Nphsc, Qampc, and Qphsc (S305). The second correction unit 262 calculates the burst offset BstPos1 based on an algorithm similar to the algorithm used in the process of S203 shown in FIG.

[0109] In the processor 26, the burst offset BstPos1 is added to the cylinder address acquired by the Gray code demodulation unit 251. The third correction unit 263 executes RRO correction on the first servo demodulation position obtained by adding the burst offset BstPos1 and the cylinder address (S306). The second servo demodulation position is obtained by the RRO correction on the first servo demodulation position.

[0110] Processor 26 uses the second servo demodulation position as the current position of magnetic head 22 to perform positioning to bring magnetic head 22 closer to the target data track (S307). Then, the operation when magnetic head 22 passes a certain servo sector SV during a write operation ends. SoC 30 can position magnetic head 22 on the target data track by repeatedly executing the processes of S301 to S307 during a write operation.

[0111] Next, a more specific example of the correction setting information 300 and the effect of correction using the correction setting information 300 will be described.

[0112] Fig. 11 is a diagram showing an example of the amplitude Namp0 of the demodulated signal of the N burst and the amplitude Qamp0 of the demodulated signal of the Q burst among the burst demodulation value set during non-write operation acquired by the process of S101 shown in Fig. 8. In this figure, the horizontal axis indicates the radial offset amount from a certain servo track 41, and the vertical axis indicates the amplitude.

[0113] Fig. 12 is a diagram showing an example of a phase Nphs0 of a demodulated signal of an N burst and a phase Qphs0 of a demodulated signal of a Q burst among the burst demodulated value sets during a non-write operation acquired by the process of S101 shown in Fig. 8. In this figure, the horizontal axis indicates the radial offset amount from a certain servo track 41, and the vertical axis indicates the phase.

[0114] Fig. 13 is a diagram showing an example of the amplitude Namp1 of the demodulated signal of the N burst and the amplitude Qamp1 of the demodulated signal of the Q burst among the burst demodulated value set during the write operation acquired by the process of S102 shown in Fig. 8. In this figure, the horizontal axis indicates the radial offset amount from a certain servo track 41, and the vertical axis indicates the amplitude.

[0115] Fig. 14 is a diagram showing an example of a phase Nphs1 of a demodulated signal of an N burst and a phase Qphs1 of a demodulated signal of a Q burst among the burst demodulated value sets during a write operation acquired by the process of S102 shown in Fig. 8. In this figure, the horizontal axis indicates the radial offset amount from a certain servo track 41, and the vertical axis indicates the phase.

[0116] 11 and 13, it can be seen that the amplitude is slightly different during non-write operations and during write operations. Also, when Fig. 12 and 14 are compared, it can be seen that the phase is slightly different during non-write operations and during write operations.

[0117] FIG. 15 is a graph plotting the burst data Nbst1, Qbst1 after initial phase correction calculated from the burst demodulation value set during non-write operation and the burst data Nbst1, Qbst1 after initial phase correction calculated from the burst demodulation value set during write operation without correction using the correction setting information 300 on a two-dimensional plane. The horizontal axis of this graph is the N burst data axis, and the vertical axis is the Q burst data axis. The waveform plotted on such a graph is also called a Lissajous waveform. As shown in this figure, it can be seen that the burst data Nbst1, Qbst1 after initial phase correction calculated from the burst demodulation value set during non-write operation and the burst data Nbst1, Qbst1 after initial phase correction calculated from the burst demodulation value set during write operation without correction using the correction setting information 300 do not match.

[0118] Fig. 16 is a diagram showing an example of the amplitude ratios Ngain and Qgain in the correction setting information 300 obtained by the process of S103 shown in Fig. 8. In this diagram, the horizontal axis indicates the radial offset amount from a certain servo track 41, and the vertical axis indicates the magnitude of the amplitude ratio. If the amplitude is equal during non-write operation and during write operation, the amplitude ratio should be 1. However, in reality, the amplitude is slightly different during non-write operation and during write operation, so as shown in this diagram, the amplitude ratio is slightly deviated from 1.

[0119] Fig. 17 is a diagram showing an example of phase differences Nphsofs and Qphsofs in the correction setting information 300 obtained by the process of S103 shown in Fig. 8. In this diagram, the horizontal axis indicates the radial offset amount from a certain servo track 41, and the vertical axis indicates the magnitude of the phase difference. If the phase is the same during non-write operation and during write operation, the phase difference should be 0. However, in reality, the phase is slightly different during non-write operation and during write operation, so as shown in this diagram, the phase difference is slightly deviated from 0.

[0120] 18 is a diagram showing an example of the difference between the second servo demodulation position calculated from the burst demodulation value set during non-write operation and the second servo demodulation position calculated from the burst demodulation value set during write operation without correction using the correction setting information 300, observed in a certain servo track 41 or a plurality of servo sectors SV on a certain data track. From this diagram, it can be seen that the difference between the burst demodulation value set during non-write operation and the burst demodulation value set during write operation is not eliminated, causing a difference between the second servo demodulation positions.

[0121] 19 is a diagram showing an example of observing the difference between the second servo demodulation position calculated from the burst demodulation value set during non-write operation and the second servo demodulation position calculated by performing correction using the correction setting information 300 from the burst demodulation value set during write operation in a certain servo track 41 or a plurality of servo sectors SV on a certain data track. From this figure, it can be seen that the difference between the second servo demodulation position during non-write operation and the second servo demodulation position during write operation is greatly suppressed as a result of performing correction using the correction setting information 300 on the burst demodulation value set during write operation.

[0122] As described above, the RRO correction amount recorded as the postcode is learned during a non-write operation. In other words, when the RRO correction is performed during a non-write operation, the error due to the RRO between the target track and the position of the magnetic head 22 can be most effectively suppressed. According to the embodiment, the difference between the second servo demodulation position during a non-write operation and the second servo demodulation position during a write operation can be significantly suppressed, so that the error due to the RRO can be effectively suppressed during a write operation as well as during a non-write operation. In other words, the error between the target track and the position of the magnetic head during a write operation can be suppressed. As a result, the designer can reduce the data track pitch and increase the storage capacity of the magnetic disk device 1.

[0123] As described above, according to the embodiment, in a write operation, that is, an operation of writing to the data area DA while positioning the magnetic head 22, the SoC 30 operates as follows. That is, the SoC 30 demodulates the burst pattern to obtain a burst demodulation value set. Then, the SoC 30 corrects the burst demodulation value set based on a correction algorithm that uses the correction setting information 300 as an argument. Then, the SoC 30 calculates a burst offset based on the corrected burst demodulation value set.

[0124] Since the burst demodulation value set during a write operation can be made closer to the burst demodulation value set during a non-write operation, it is possible to suppress the deterioration of the position error RPE during a write operation. As a result, the designer can reduce the data track pitch and increase the storage capacity of the magnetic disk device 1.

[0125] In addition, in a non-write operation, i.e., an operation in which the magnetic head 22 is positioned but no writing is performed to the data area DA, the SoC 30 demodulates the burst pattern to obtain a burst demodulation value set, and calculates a burst offset based on the burst demodulation value set without making any correction to the burst demodulation value set.

[0126] Also, according to the embodiment, as described with reference to Fig. 8, while positioning the magnetic head 22 without writing to the data area DA, the SoC 30 demodulates the burst pattern at the positioning to obtain a burst demodulation value set during the non-write operation. While writing to the data area DA and positioning the magnetic head 22, the SoC 30 demodulates the burst pattern at the positioning to obtain a burst demodulation value during the write operation. Then, the SoC 30 calculates the correction setting information 300 based on the burst demodulation value set during the non-write operation and the burst demodulation value set during the write operation, and stores the correction setting information 300 in a memory (e.g., FROM 28).

[0127] Therefore, during a write operation, based on the correction setting information 300 prepared in advance, it is possible to perform a correction on the burst demodulation value set output from the burst demodulation unit 252 to bring it closer to the burst demodulation value set during a non-write operation.

[0128] Moreover, according to the embodiment, the servo data includes a postcode indicating an amount of RRO correction. The amount of RRO correction is obtained while positioning the magnetic head 22 without performing writing. The SoC 30 further performs correction based on the postcode in positioning the magnetic head 22.

[0129] Therefore, the RRO can be appropriately corrected during non-write operation. As described above, during a write operation, the burst demodulation value set output from the burst demodulation unit 252 can be corrected to approach the burst demodulation value set during non-write operation. Therefore, even during a write operation, the RRO can be appropriately corrected in the same way as during a non-write operation.

[0130] Also, as described above, in the embodiment, the SoC 30 may calculate the correction setting information 300 for each of the plurality of servo sectors and store it in the memory. Alternatively, the SoC 30 may calculate the correction setting information 300 for each of two or more servo sectors SV among the plurality of servo sectors SV, or for each of two or more servo tracks 41 among the plurality of servo tracks 41, and store it in the memory.

[0131] According to the embodiment, the burst demodulation value set includes the amplitude and phase of the demodulated signal of the burst pattern, the correction setting information 300 includes the amplitude ratios Ngain and Qgain to be multiplied by the amplitude and the phase differences Nphsofs and Qphsofs to be added to or subtracted from the phase, and the correction algorithm is an algorithm for correcting the amplitude and phase included in the burst demodulation value set based on the correction setting information 300. The SoC 30 may be configured to correct only one of the amplitude and phase included in the burst demodulation value set during a write operation.

[0132] For example, when the SoC 30 is configured to correct only the amplitude of the amplitude and phase included in the burst demodulation value set, the correction setting information 300 is configured to include the amplitude ratio (i.e., Ngain and Qgain) and not include the phase difference (i.e., Nphsofs and Qphsofs). Then, the SoC 30 corrects the amplitude included in the burst demodulation value set based on the amplitude ratio (i.e., Ngain and Qgain) included in the correction setting information 300 and the correction algorithm shown in Equation 11 and Equation 12.

[0133] In another example, when the SoC 30 is configured to correct only the phase of the amplitude and phase included in the burst demodulation value set, the correction setting information 300 is configured to include the phase difference (i.e., Nphsofs and Qphsofs) without including the amplitude ratio (i.e., Ngain and Qgain). Then, the SoC 30 corrects the phase included in the burst demodulation value set based on the phase difference (i.e., Nphsofs and Qphsofs) included in the correction setting information 300 and the correction algorithm shown in Equation 13 and Equation 14.

[0134] Fig. 20 is a diagram showing an example of the difference between the second servo demodulation position calculated from the burst demodulation value set during non-write operation and the second servo demodulation position calculated by correcting only the amplitude from the burst demodulation value set during write operation, observed in a certain servo track 41 or a plurality of servo sectors SV on a certain data track.Comparing this figure with Fig. 18, it can be seen that even if only the amplitude is corrected, the difference between the second servo demodulation position during non-write operation and the second servo demodulation position during write operation can be suppressed.

[0135] Even if only the phase is corrected for the burst demodulation value set during a write operation, the difference between the second servo demodulation position during a non-write operation and the second servo demodulation position during a write operation can be suppressed.

[0136] In this manner, the burst demodulation value set may include the amplitude and phase of the demodulated signal of the burst pattern, the correction setting information 300 may include an amplitude ratio or a phase difference, and the correction algorithm may be an algorithm that corrects the amplitude or phase included in the burst demodulation value set based on the correction setting information 300.

[0137] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0138] 1 magnetic disk device, 2 host, 11 magnetic disk, 12 SPM, 13 lamp, 15 actuator arm, 16 VCM, 21 SVC, 22 magnetic head, 22r read head, 22w write head, 23 HDC, 24 preamplifier, 25 RWC, 26 processor, 28 FROM, 29 DRAM, 30 controller, 41 servo track, 251 gray code demodulation unit, 252 burst demodulation unit, 261 first correction unit, 262 second correction unit, 263 third correction unit, 264 correction setting information generation unit, 300 correction setting information.

Claims

1. a magnetic disk including a plurality of servo tracks, a plurality of servo sectors on which servo data including burst patterns are recorded, the servo tracks being spaced apart in a circumferential direction, and a data area in which data is written is disposed between the servo sectors arranged in the circumferential direction; a magnetic head for writing and reading data to and from the magnetic disk; A memory in which a first setting value is stored; a controller that, in a first operation for writing to the data area while positioning the magnetic head, demodulates the burst pattern to obtain a first burst demodulation value, corrects the first burst demodulation value based on a correction algorithm that uses the first setting value as an argument, and calculates an offset amount of the magnetic head from one of the plurality of servo tracks based on a second burst demodulation value that is the corrected first burst demodulation value; A magnetic disk device comprising:

2. In a second operation in which the controller positions the magnetic head but does not write to the data area, the controller demodulates the burst pattern to obtain a third burst demodulation value, and calculates an offset amount of the magnetic head from one of the plurality of servo tracks based on the third burst demodulation value.

2. The magnetic disk drive according to claim 1.

3. the controller demodulates the burst pattern while attempting to position the magnetic head without writing to the data area to obtain a fourth burst demodulated value, demodulates the burst pattern while attempting to position the magnetic head while writing to the data area to obtain a fifth burst demodulated value, calculates the first setting value based on the fourth burst demodulated value and the fifth burst demodulated value, and stores the first setting value in the memory.

3. The magnetic disk drive according to claim 1.

4. each of the first burst demodulation value, the fourth burst demodulation value, and the fifth burst demodulation value includes an amplitude and a phase of a demodulated signal of the burst pattern; the first set value is an amplitude ratio or a phase difference, the amplitude ratio is a ratio between an amplitude included in the fourth burst demodulation value and an amplitude included in the fifth burst demodulation value, the phase difference is a difference between a phase included in the fourth burst demodulated value and a phase included in the fifth burst demodulated value, The correction algorithm is an algorithm for correcting an amplitude or a phase included in the first burst demodulation value based on the first set value.

4. The magnetic disk drive according to claim 3.

5. the first burst demodulation value includes an amplitude and a phase of a demodulated signal of the burst pattern; the first set value includes a set value to be multiplied by the amplitude or a set value to be added to or subtracted from the phase, the correction algorithm is an algorithm that corrects the amplitude or the phase based on the first set value.

2. The magnetic disk drive according to claim 1.

6. the servo data further includes a postcode having correction data for correcting a repeatable runout (RRO), the correction data for correcting the RRO being an RRO correction amount calculated based on data obtained by measuring the positioning of the magnetic head without writing data to the data area; the controller further performs head positioning correction based on the RRO correction data acquired from the postcode in positioning the magnetic head.

2. The magnetic disk drive according to claim 1.

7. the controller calculates the first setting value for each of the plurality of servo sectors and stores the first setting value in the memory; 4. The magnetic disk drive according to claim 3.

8. the controller calculates a plurality of the first setting values ​​for each of two or more servo sectors among the plurality of servo sectors, or for each of two or more servo tracks among the plurality of servo tracks, and stores an average value of the plurality of first settings in the memory; 4. The magnetic disk drive according to claim 3.

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