Magnetic disk device

Abstract

Provided is a magnetic disk device capable of appropriately determining whether or not residual vibration of a magnetic head due to a seek operation has sufficiently attenuated. A controller of a magnetic disk device moves a magnetic head to a first track, which is one of a plurality of tracks. The controller acquires a positioning error amount from the head of the first track at a servo sampling period. The controller performs access to the first track using the magnetic head after obtaining a positioning error amount equal to or less than a first threshold value for a first set number of consecutive times. The controller estimates a frequency of residual vibration of the magnetic head caused by movement of the magnetic head to the first track and an amplitude of the residual vibration. The controller updates the first set number of times on the basis of the frequency estimation value of the residual vibration and the amplitude estimation value of the residual vibration.

Description

[0001] This application claims the priority of Japanese Patent Application No. 2023-157434 (filing date: September 22, 2023) as a basic application. The present application incorporates all the contents of the basic application by reference. Technical Field

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

[0003] In a magnetic disk device, when a seek operation is performed, a write operation or a read operation is performed on a target track after residual vibration of the magnetic head is sufficiently attenuated. Summary of the invention

[0004] An embodiment of the present invention provides a magnetic disk device capable of appropriately determining whether or not residual vibration of a magnetic head caused by a seek operation has been sufficiently attenuated.

[0005] The magnetic disk device involved in this embodiment includes a magnetic disk, a magnetic head and a controller. The magnetic disk has a plurality of tracks. The controller moves the magnetic head to the first track which is one of the plurality of tracks. The controller obtains the positioning error amount of the magnetic head from the first track in a servo sampling cycle. After the controller obtains the positioning error amount below the first threshold value for a first set number of times in a row, the controller uses the magnetic head to perform access to the first track. The controller estimates the frequency of the residual vibration of the magnetic head caused by the movement of the magnetic head to the first track and the amplitude of the residual vibration. The controller updates the first set number of times based on the estimated value of the frequency of the residual vibration and the estimated value of the amplitude of the residual vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 This is a schematic diagram showing an example of the configuration of the magnetic disk device according to the first embodiment.

[0007] Figure 2 This is a diagram showing an example of the structure of the magnetic disk according to the first embodiment.

[0008] Figure 3 This is a diagram for explaining a settling operation according to the first embodiment.

[0009] Figure 4 This is a diagram for explaining an example of a method for determining a stable count according to the first embodiment.

[0010] Figure 5 This is a diagram for explaining another example of the method for determining the stable count according to the first embodiment.

[0011] Figure 6This is a flowchart for explaining an example of the operation related to the seek operation in the first embodiment.

[0012] Figure 7 This is a flowchart for explaining an example of the learning operation according to the first embodiment.

[0013] Figure 8 This is a flowchart for explaining an example of the operation of the magnetic disk device 1 according to the second embodiment.

[0014] Fig. 9 This is a diagram for explaining the relationship between the stable count and the guaranteed width.

[0015] Fig.10 This is a flowchart for explaining an example of the operation of the magnetic disk device 1 according to the third embodiment.

[0016] Fig.11 This is a flowchart for explaining an example of the operation of the magnetic disk device 1 according to the fourth embodiment.

[0017] Description of symbols

[0018] 1 disk device; 2 host; 11 disk; 12 spindle motor; 13 ramp; 15 actuator arm; 16 VCM; 21 motor driver IC; 22 head; 22r read element; 22w write element; 23 HDC; 24 head IC; 25 RWC; 26 processor; 27 RAM; 28 FROM; 30 controller; 41 servo area; 42 data area; 50 track. DETAILED DESCRIPTION

[0019] Hereinafter, the magnetic disk device according to the embodiment will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments.

[0020] (First embodiment)

[0021] Figure 1 It is a schematic diagram showing an example of the configuration of the magnetic disk device 1 according to the first embodiment.

[0022] The magnetic disk device 1 can be connected to a host 2. When connected to the host 2, the magnetic disk device 1 can receive an access command from the host 2. The access command is a write command, a read command, or the like.

[0023] The magnetic disk device 1 includes a magnetic disk 11 having a magnetic layer formed on the surface thereof. The magnetic disk device 1 writes data to the magnetic disk 11 and reads data from the magnetic disk 11 in accordance with an access command.

[0024] Data is written and read via a magnetic head 22. The magnetic disk device 1 includes a spindle motor 12, a ramp 13, an actuator arm 15, a voice coil motor (VCM) 16, a motor driver IC (Integrated Circuit) 21, a magnetic head 22, a hard disk controller (HDC) 23, a head IC 24, a read / write channel (RWC) 25, a processor 26, a RAM 27, and a FROM (Flash Read Only Memory) 28 in addition to the magnetic disk 11.

[0025] The magnetic disk 11 is rotated at a predetermined rotation speed by a coaxially mounted spindle motor 12 . The spindle motor 12 is driven by a motor driver IC 21 .

[0026] The processor 26 controls the rotation of the spindle motor 12 and the rotation of the VCM 16 via the motor driver IC 21 .

[0027] The magnetic head 22 writes and reads information to and from the magnetic disk 11 through the write element 22w and the read element 22r it has. In addition, the magnetic head 22 is installed at the front end of the actuator arm 15. The magnetic head 22 moves in the radial direction of the magnetic disk 11 through the VCM 16. In addition, either one or both of the write element 22w and the read element 22r of the magnetic head 22 can be provided with a plurality of them respectively with respect to a single magnetic head 22.

[0028] When the rotation of the magnetic disk 11 stops, the magnetic head 22 is moved onto the ramp 13 . The ramp 13 is configured to hold the magnetic head 22 at a position away from the magnetic disk 11 .

[0029] During a write operation, the head IC 24 amplifies a signal corresponding to the write target data supplied from the RWC 25 and supplies it to the magnetic head 22. During a read operation, the head IC 24 amplifies and outputs a signal read from the magnetic disk 11 by the magnetic head 22 and supplies it to the RWC 25.

[0030] The HDC 23 controls data transmission and reception with the host computer 2 via the I / F bus.

[0031] The RAM 27 is used as a buffer for data to be written to the magnetic disk 11 and data read from the magnetic disk 11. In addition, a command queue for storing access commands received from the host 2 is provided in the RAM 27.

[0032] The RAM 27 is used as an operation memory by the processor 26. The RAM 27 is used as an area for loading firmware and an area for temporarily storing various management data.

[0033] RAM 27 is composed of a volatile memory capable of high-speed operation. The type of memory constituting RAM 27 is not limited to a specific type. RAM 27 can be composed of, for example, DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), or a combination thereof.

[0034] The RWC 25 performs data conversion such as error correction coding and modulation coding on the data to be written supplied from the HDC 23 in units of sectors, and supplies the data after these data conversions to the head IC 24. In addition, the RWC 25 performs processing such as error correction and demodulation on the signal read from the magnetic disk 11 and supplied from the head IC 24 in units of sectors, and outputs the processed signal to the HDC 23 as digital data.

[0035] The processor 26 is, for example, a CPU (Central Processing Unit) and is connected to a RAM 27 and a FROM (Flash Read Only Memory) 28 .

[0036] FROM 28 is a nonvolatile memory that stores firmware (program data) and various operating parameters.

[0037] The processor 26 controls the entire magnetic disk device 1 according to the firmware stored in the FROM 28. For example, the processor 26 loads the firmware from the FROM 28 to the RAM 27, and controls the motor driver IC 21, the head IC 24, the RWC 25, and the HDC 23 according to the loaded firmware.

[0038] The firmware program may also be stored in the disk 11. In addition, part or all of the functions of the processor 26 may also be implemented by a hardware circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0039] The configuration including the HDC 23, the RWC 25, and the processor 26 can also be regarded as a controller 30 that controls the operation of the magnetic disk device 1. The controller 30 may include other elements (for example, a RAM 27 or a FROM 28) in addition to these.

[0040] In addition, the firmware program may be stored in the magnetic disk 11. In addition, part or all of the functions of the processor 26 may be realized by a hardware circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0041] In addition, the number of magnetic disks 11 provided in the magnetic disk device 1 is not limited to one. In addition, the magnetic disk device 1 may have the actuator arms 15 and magnetic heads 22 in the number corresponding to the number of magnetic disks 11. In addition, when the magnetic disk device 1 has a plurality of magnetic heads 22, the plurality of magnetic heads 22 may move in an integral manner, or the plurality of magnetic heads 22 may constitute a plurality of groups that can move independently of each other.

[0042] Figure 2 This is a diagram showing an example of the structure of the magnetic disk 11 according to the first embodiment. Servo data used for positioning the magnetic head 22 is written on the magnetic layer formed on the surface of the magnetic disk 11 by, for example, a servo writer or self servo writing (SSW).

[0043] exist Figure 2 1, as an example of the configuration of the servo area in which the servo data is written, a servo area 41 arranged in a radial shape is shown. In the circumferential direction, a data area 42 in which data can be written is set between two servo areas 41. A plurality of concentric tracks 50 are set in the radial direction of the magnetic disk 11. On the tracks 50, a plurality of sectors are set in the data area 42, each of which has data of a predetermined size written therein. The predetermined size is the sector size.

[0044] The servo data is data used to estimate the current position of the magnetic head 22 . The controller 30 performs positioning control of the magnetic head 22 based on the servo data read by the magnetic head 22 from the servo area 41 .

[0045] When the controller 30 uses the magnetic head 22 to access (write or read) the magnetic disk 11, it first moves the magnetic head 22 in the radial direction toward the target track. The target track is the access target track 50. The operation of moving the magnetic head 22 in the radial direction toward the target track is referred to as a seek operation.

[0046] When the magnetic head 22 is moved to a target track by a seek operation, residual vibration of the magnetic head 22 is generated. If the residual vibration is large, the controller 30 cannot perform access correctly.

[0047] For example, in a write operation, the controller 30 determines whether the magnetic head 22 is in an on-track state (that is, it is regarded as a state where the magnetic head 22 is located on the target track). When it is presumed that the magnetic head 22 is not in an on-track state, the controller 30 interrupts the write operation immediately. And, after the disk 11 rotates one circle, the controller 30 performs a retry (retry write operation) of the write operation. Whether the magnetic head 22 is in an on-track state in the write operation is determined by comparing the positioning error amount with a write off track piece. When the positioning error amount exceeds the write off track piece, the controller 30 interrupts the write operation immediately and retry the write operation. When the write operation is started under a large residual vibration state, the positioning error amount exceeds the write off track piece and the risk of the write operation being interrupted is high.

[0048] Therefore, the controller 30 performs a stabilization operation after the seek operation, which is an operation of waiting until the residual vibration is sufficiently attenuated. After the stabilization operation, the controller 30 performs access to the target track.

[0049] Figure 3 This is a diagram for explaining the stabilization operation of the first embodiment.

[0050] In the stable operation, the threshold value Th is used to determine whether the residual vibration of the magnetic head 22 has been sufficiently attenuated. stl . Set the threshold Th stl Recorded as the stability threshold Th stl In addition, the stability threshold Th stl is an example of the first threshold.

[0051] The controller 30 compares the positioning error with the stability threshold Th stl By comparison, it is determined whether the radial position of the magnetic head 22 is within the -Th based on the track center (center) of the target track. stl ~+Th stl within the range.

[0052] In addition, Figure 3 In FIG. 1 , the radial position is expressed with the outer circumference being the negative direction and the inner circumference being the positive direction. The setting of the negative direction and the positive direction at the radial position is not limited to this.

[0053] In one example, the controller 30 moves the magnetic head 22 to a target track in a seek operation when the positioning error amount reaches the stable threshold value Th for the first time. stl The following timing (for example Figure 3 At the timing t1), the stabilization action begins.

[0054] During the stable operation, the controller 30 obtains the positioning error and maintains it at the stable threshold value Th stlThe length of the following period. When the positioning error is maintained at the stable threshold value Th stl When the length of the following period reaches the preset stabilization time, the controller 30 ends the stabilization operation and becomes a state in which a write operation to the target track can be performed.

[0055] As described above, the controller 30 obtains the positioning error amount based on the servo data read from the magnetic disk 11. That is, the controller 30 successively obtains the positioning error amount at the cycle when the magnetic head 22 passes through the servo area 41, that is, the servo sampling cycle. Thus, the controller 30 uses the continuously obtained stable threshold value Th stl The number of times the positioning error is maintained at the stable threshold value Th is stl In other words, the stable threshold value Th is continuously obtained. stl The following positioning error is the number of times the stable threshold Th is continuously obtained. stl The following is the servo sampling number of the positioning error amount. The servo sampling number is the number of times the servo data is acquired.

[0056] The controller 30 obtains the stable threshold value Th stl When the positioning error is less than the following, the count value of the servo sampling number is incremented. stl When the positioning error is greater than 100, the controller 30 resets the count value to zero. By repeating these processes, the stable threshold value Th is continuously obtained. stl The controller 30 counts the number of positioning errors as follows. When the count value reaches a value corresponding to the stabilization time, the controller 30 ends the stabilization operation.

[0057] Hereinafter, the number of times corresponding to the settling time will be described as a settling count. In addition, the settling time is equivalent to a value obtained by multiplying the settling count by the servo sampling period.

[0058] exist Figure 3 In the example shown, the positioning error amount becomes the stable threshold value Th stl From the following timing t2 to the timing t3 after the stabilization time, all the positioning errors obtained are maintained at the stable threshold value Th stl As a result, the controller 30 ends the stabilization operation at timing t3 and performs the write operation to the target track.

[0059] In addition, Figure 3 The figure shows the deviation image (Th WOS ) corresponding to the line. When the radius position of the magnetic head 22 is -Th based on the center of the target track WOS ~+Th WOSWhen the range is exceeded, the controller 30 interrupts the write operation and performs a retry write operation. Figure 3 In the example shown, the offset piece Th is written WOS Set as the stability threshold Th stl Big, but write off-track film Th WOS and the stability threshold Th stl The size relationship of is not limited to this. WOS and the stability threshold Th stl Can also be the same.

[0060] A technology compared with the embodiment will be described. A technology compared with the embodiment will be described as a comparative example.

[0061] According to the comparative example, the stabilization count is determined at the time of design. After shipment, the magnetic disk device performs a stabilization operation using the stabilization count determined at the time of design.

[0062] However, the behavior of the residual vibration caused by the seek action may change according to environmental factors and changes over the years. Environmental factors are the temperature in the set environment, the vibration received from the set environment, the fixing method of the disk device, etc. Due to the change in the behavior of the residual vibration caused by the seek action, the stable count determined at the time of design sometimes becomes insufficient to determine whether the residual vibration has been fully attenuated. That is, even if the stable action has ended, the residual vibration may not be fully attenuated. In this case, sometimes the positioning error amount exceeds the write deviation piece immediately shortly after the write action starts, causing the write action to stop.

[0063] If a sufficiently large value is set as the stable count during design so that the stable count does not become insufficient, the write operation can be prevented from stopping immediately after the write operation starts. However, when the stable count is too large, the seek time (i.e., the time required for the seek operation) will become longer and the performance of the disk device will decrease.

[0064] Therefore, in the first embodiment, the controller 30 is configured to autonomously determine the stable count according to the behavior of the residual vibration. More specifically, the controller 30 estimates the frequency and amplitude of the residual vibration during the stable operation, and determines the set value of the stable count based on the estimated value of the frequency and the estimated value of the amplitude.

[0065] Figure 4 1 is a diagram for explaining an example of a method for determining a stable count of the first embodiment. In this figure, the time transition of the radial position of the magnetic head 22 when the magnetic head 22 vibrates in the radial direction at a certain frequency is depicted. In addition, the vertical axis represents the radial position of the magnetic head 22, and the horizontal axis represents the servo sampling number.

[0066] Figure 4The time length of one cycle of the vibration shown corresponds to the servo sampling number "15." Therefore, the controller 30 sets the servo sampling number "15" as the stable count.

[0067] In this way, by setting the number of servo samplings corresponding to one cycle of vibration as the stable count, it is possible to confirm that the maximum value of the positioning error amount is the stable threshold value Th. stl This ensures that the vibration amplitude after the stabilization operation ends reaches the stabilization threshold value Th. stl The following can prevent the positioning error amount from exceeding the write track plate due to residual vibration after the writing action starts.

[0068] Furthermore, when the residual vibration includes two vibrations with large amplitudes and different frequencies, a beat may be generated by the two vibrations. In such a case, even if the servo sampling number corresponding to the time length of one cycle of either of the two vibrations is set as the stable count, it cannot be guaranteed that the vibration amplitude after the stable operation ends will become the stable threshold value Th. stl the following.

[0069] According to the first embodiment, it is configured that the number of servo samples corresponding to one cycle of the beat can also be set as the stable count.

[0070] Figure 5 This is a diagram for explaining another example of the method for determining the stable count according to the first embodiment. The vertical axis represents the radial position of the magnetic head 22, and the horizontal axis represents the servo sampling number.

[0071] exist Figure 5 In the example shown, the residual vibration of the magnetic head 22 includes two vibrations with substantially the same amplitude and different frequencies, thereby generating a large beat in the residual vibration of the magnetic head 22. Moreover, one cycle of the beat is equivalent to the servo sampling number "45". Therefore, the controller 30 sets the servo sampling number "45" as the stable count.

[0072] The number of servo samplings corresponding to one cycle of the beat is set as the stable count. Thus, even when a beat occurs, the maximum value of the positioning error amount can be confirmed as the stable threshold value Th. stl The stabilization operation ends in the following situation.

[0073] Next, an example of the operation of the magnetic disk device 1 according to the first embodiment will be described. It is assumed here that the controller 30 is configured to be able to estimate the frequency and amplitude of two vibrations among the plurality of vibrations included in the residual vibration.

[0074] Figure 6This is a flowchart for explaining an example of the operation related to the seek operation in the first embodiment. Here, the operation related to the seek operation for executing the write operation will be explained.

[0075] The controller 30 first obtains the set value C of the stable count set , start the seek operation (S101). The set value C of the stable count set The controller 30 reads the set value C of the stable count from the predetermined storage area. set In addition, the predetermined storage area is RAM 27, FROM 28, or any area other than these.

[0076] The controller 30 determines whether the positioning error amount has reached the stable threshold value Th stl Next (S102). If the determination result in S102 is "NO", the controller 30 executes the determination process in S102 again.

[0077] If the determination result in S102 is YES, the controller 30 starts a learning operation for learning the stable count (S103), and starts a stable operation. The details of the learning operation will be described later.

[0078] In the stable operation, the controller 30 determines whether the continuous C set The stability threshold Th stl The following positioning error amount (S104).

[0079] When a “NO” determination is made in the determination process of S104 , the controller 30 executes the determination process of S104 again.

[0080] When a “YES” determination is made in the determination process of S104 , the controller 30 ends the learning operation ( S105 ).

[0081] The controller 30 updates the set value C with the learning value C of the stable count obtained through the learning action. set (S106) Then, the controller 30 starts a write operation for the target track (S107), and a series of operations associated with the seek operation are completed.

[0082] Figure 7 This is a flowchart for explaining an example of the learning operation according to the first embodiment.

[0083] exist Figure 7In the example shown, the controller 30 uses C, C1, C2, and C3 as parameters associated with the stable count. As described above, the controller 30 estimates the frequency and amplitude of two vibrations of different frequencies included in the residual vibration. One of the two vibrations is recorded as the first vibration, and the other of the two vibrations is recorded as the second vibration. Parameter C1 is a parameter that temporarily sets the learning value of the stable count that only takes into account the first vibration. Parameter C2 is a parameter that temporarily sets the learning value of the stable count that only takes into account the second vibration. Parameter C3 is a parameter that temporarily sets the learning value of the stable count that only takes into account the beat generated by the first vibration and the second vibration.

[0084] Hereinafter, the estimated value of the frequency of the first vibration is recorded as frequency estimated value f1, and the estimated value of the frequency of the second vibration is recorded as frequency estimated value f2. The estimated value of the amplitude of the first vibration is recorded as amplitude estimated value a1, and the estimated value of the amplitude of the second vibration is recorded as amplitude estimated value a2.

[0085] First, the controller 30 sets the initial setting value C0 of the stable count for parameter C, and sets parameters C1, C2, and C3 to 0 (S201). C0 is determined by the designer at the time of design, for example, and is stored in a predetermined storage area. In S201, the controller 30 reads C0 from the predetermined storage area.

[0086] Next, the controller 30 estimates the frequency and amplitude of the vibration included in the residual vibration based on the positioning error amount obtained successively. The controller 30 has two frequency / amplitude estimators. The controller 30 estimates the frequency f1 and amplitude a1 of the first vibration and the frequency f2 and amplitude a2 of the second vibration by using the two frequency / amplitude estimators (S202).

[0087] In addition, as an algorithm for estimating the frequency and amplitude by the frequency / amplitude estimator, any algorithm can be applied. In one example, the frequency / amplitude estimator can also be configured as an adaptive filter that estimates the frequency and amplitude. In another example, the frequency / amplitude estimator can also be configured to estimate the frequency and amplitude by discrete Fourier transform.

[0088] The controller 30 calculates the stable count for each of the first vibration and the second vibration only when the corresponding amplitude estimation value is large. For this purpose, a threshold value (referred to as an amplitude threshold value) to be compared with the amplitude of each vibration is set in advance.

[0089] exist Figure 7 In the example shown, Th is set as the amplitude threshold value to be compared with the amplitude estimation value a1. a11 ,Th a12 As the amplitude threshold value to be compared with the amplitude estimation value a2, Th is set. a21 ,Tha22 Amplitude threshold Th a11 Ratio amplitude threshold Th a12 Large. Amplitude threshold Th a21 Ratio amplitude threshold Th a22 In addition, the amplitude threshold Th a11 ,Th a12 ,Th a21 ,Th a22 This is an example of the second threshold.

[0090] The controller 30 determines whether the amplitude estimation value a1 is greater than the amplitude threshold value Th. a11 If it is determined to be YES in the determination process of S203, the controller 30 sets the parameter C1 to a value obtained by dividing the servo sampling frequency fs by the frequency estimation value f1 (S204).

[0091] Through the process of S204 , a stable count that can be used to determine whether the first vibration has sufficiently decayed is set in the parameter C1 .

[0092] If the determination result in step S203 is “NO”, the controller 30 determines whether the estimated amplitude value a1 is greater than the amplitude threshold value Th. a12 When it is determined as "YES" in the determination process of S205, the controller 30 sets 0 to the parameter C1 (S206).

[0093] After the process of S204, if the determination in the determination process of S205 is "No", or after the process of S206, the controller 30 determines whether the amplitude estimation value a2 is greater than the amplitude threshold value Th. a21 If it is determined to be YES in the determination process of S207, the controller 30 sets the parameter C2 to a value obtained by dividing the servo sampling frequency fs by the frequency estimation value f2 (S208).

[0094] Through the process of S208 , a stable count that can be used to determine whether the second vibration has sufficiently attenuated is set in the parameter C2 .

[0095] If the determination result in step S207 is “NO”, the controller 30 determines whether the estimated amplitude value a2 is greater than the amplitude threshold value Th. a22 When the determination result of S209 is YES, the controller 30 sets the parameter C2 to 0 (S210).

[0096] After the process of S208, if the determination in the determination process of S209 is "No", or after the process of S210, the controller 30 determines whether the amplitude estimation value a1 is greater than the amplitude threshold value Th. a11The amplitude estimation value a2 is greater than the amplitude threshold value Th. a21 Big (S211).

[0097] If it is determined as YES in the determination process of S211 , the controller 30 sets the parameter C3 to a value obtained by dividing the servo sampling frequency fs by the absolute value of the difference between the frequency estimated value f1 and the frequency estimated value f2 ( S212 ).

[0098] Through the process of S212 , a stable count that can be used to determine whether the vibration caused by the beat generated by the first vibration and the second vibration has sufficiently decayed is set in the parameter C3 .

[0099] If the determination result in step S211 is “NO”, the controller 30 determines whether the amplitude estimation value a1 is greater than the amplitude threshold value Th. a12 The amplitude estimation value a2 is smaller than the amplitude threshold value Th. a22 Small (S213).

[0100] When a “YES” determination is made in the determination process of S213 , the controller 30 sets 0 to the parameter C3 ( S214 ).

[0101] After the process of S212, when it is determined as "NO" in the determination process of S213, or after the process of S214, the controller 30 determines the maximum value among C0, C1, C2, and C3 as the learning value C of the stable count (S215).

[0102] The maximum value among C0, C1, C2, and C3 is also a value obtained by multiplying the inverse of the minimum value among the frequency f1 of the first vibration, the frequency f2 of the second vibration, and the difference between the frequency f1 and the frequency f2 by the servo sampling frequency.

[0103] Through the processing of S215, even when the residual vibration includes two vibrations of different frequencies and a large beat caused by the two vibrations occurs, a stable count is obtained that can be used to determine whether both the two vibrations and the beat vibrations have been sufficiently attenuated.

[0104] After the process of S215 , the learning operation ends.

[0105] In addition, in the above description, when a write operation is performed, Figure 6 and Figure 7 The seek action, stabilization action, and learning action shown in the figure can also be performed when the read action is performed.

[0106] In addition, Figure 7In the example shown, by using two amplitude thresholds of different sizes for the first vibration and the second vibration, a dead zone is generated for the settings of C1, C2, and C3. The dead zone is set for the settings of C1, C2, and C3 for the following reasons. That is, the processing of S202 to S215 may be repeatedly performed in a single stabilization action. When the dead zone is not set in such a case, that is, when one amplitude threshold is used for the first vibration and one amplitude threshold is used for the second vibration, the control becomes unstable. In order to prevent control instability, two amplitude thresholds of different sizes are used for the first vibration and the second vibration. In addition, one amplitude threshold may be used for the first vibration and one amplitude threshold for the second vibration.

[0107] In the above description, the controller 30 is configured to estimate the frequency and amplitude of two vibrations included in the residual vibration. The number of vibrations for which the controller 30 can estimate the frequency and amplitude may be any number as long as it is one or more.

[0108] For example, when the controller 30 can estimate the frequency and amplitude of only one vibration, the controller 30 updates the set value C of the stable count based on the estimated value of the frequency and the estimated value of the amplitude of the vibration. set Specifically, when the amplitude estimation value is greater than the amplitude threshold value, the controller 30 updates the set value C of the stable count with a value based on the frequency estimation value. set The value based on the frequency estimated value is specifically a value obtained by dividing the servo sampling frequency fs by the frequency estimated value.

[0109] In addition, for example, when the controller 30 can estimate the frequency and amplitude for two or more vibrations, the controller 30 can operate as follows. That is, when the residual vibration includes two or more vibrations whose amplitude estimation values ​​are larger than the amplitude threshold, the controller 30 updates the set value C of the stable count based on the frequency estimation value of each of the two or more vibrations and the difference between the frequency estimation values ​​of the two or more vibrations. set Specifically, the controller 30 multiplies the reciprocal of the minimum value of the difference between the frequency estimation values ​​of two or more vibrations whose amplitude estimation values ​​are larger than the amplitude threshold and the frequency estimation values ​​of the two or more vibrations by the servo sampling frequency, and updates the set value C of the stable count with the value obtained by the multiplication. set .

[0110] In the above description, a single stable count setting value C is used in common for the entire magnetic disk device 1. set The controller 30 may also be configured to store a plurality of setting values ​​C set , select multiple set values ​​C according to the conditions set The used and updated setting value C setFor example, different setting values ​​C may be used and updated for each seek distance. set Alternatively, the disk 11 may be divided into a plurality of areas in the radial direction, and different setting values ​​C may be used and updated for each area of ​​the seek destination. set Alternatively, when a plurality of magnetic heads 22 are mounted, different setting values ​​C may be used and updated for each head. set .

[0111] As described above, according to the first embodiment, the controller 30 moves the magnetic head 22 to the target track, and set The stability threshold Th stl At this time, the controller 30 estimates the frequency and amplitude of the residual vibration, and updates the set value C of the stable count based on the estimated value of the residual vibration frequency and the estimated value of the residual vibration amplitude. set .

[0112] This makes it possible to set an appropriate time length based on the frequency of the residual vibration actually caused as the stabilization time. In other words, it is possible to appropriately determine whether the residual vibration of the magnetic head 22 has been sufficiently attenuated.

[0113] According to the first embodiment, when the amplitude estimation value is larger than the amplitude threshold value, the controller 30 updates the set value C of the stable count by a value obtained by dividing the servo sampling frequency fs by the frequency estimation value. set .

[0114] According to the first embodiment, when the residual vibration includes two or more vibrations whose amplitude estimation values ​​are larger than the amplitude threshold, the controller 30 updates the set value C of the stable count based on the frequency estimation values ​​of each of the two or more vibrations and the difference between the frequency estimation values ​​of the two or more vibrations. set Specifically, the controller 30 multiplies the reciprocal of the minimum value of the difference between the frequency estimation values ​​of two or more vibrations whose amplitude estimation values ​​are larger than the amplitude threshold and the frequency estimation values ​​of the two or more vibrations by the servo sampling frequency, and updates the set value C of the stable count with the value obtained by the multiplication. set .

[0115] Thus, even when a large beat is generated due to multiple vibrations, it is possible to ensure that the vibration amplitude after the stabilization operation ends reaches the stabilization threshold value Th. stl As a result, it is possible to prevent the positioning error amount from exceeding the write deviation plate due to residual vibration after the writing operation starts.

[0116] (Second embodiment)

[0117] The servo data used to obtain the positioning error amount can only be obtained from a plurality of servo areas 42 that are spaced apart and configured in the circumferential direction. Thus, when the magnetic head 22 is located between the servo areas 42, the controller 30 cannot obtain the radial position. Thus, even if the positioning error amount is confirmed to be below the write deflection track piece based on the servo data, the radial position of the magnetic head 22 may sometimes be different from the -Th based on the center of the track due to interference, etc. WOS ~+Th WOS The position of the magnetic head 22 is out of the range of -Th WOS ~+Th WOS Exiting the range is called overrun.

[0118] Due to the overtravel, the radial position of the magnetic head 22 changes from -Th based on the center of the track. WOS ~+Th WOS The distance of the range of separation is proportional to the maximum speed in the radial direction of the magnetic head 22. Moreover, the maximum speed in the radial direction of the magnetic head 22 after the stable operation depends on the frequency and amplitude of the residual vibration. The larger the frequency of the residual vibration, the faster the maximum speed in the radial direction of the magnetic head 22 after the stable operation, and the larger the amplitude of the residual vibration, the faster the maximum speed in the radial direction of the magnetic head 22 after the stable operation.

[0119] In the second embodiment, the controller 30 updates the set value C of the stable count. set , and perform a stable threshold Th stl Or write the off-track film Th WOS Updates.

[0120] In the following description of the second embodiment, description of matters that are the same as those of the first embodiment will be omitted.

[0121] Figure 8 This is a flowchart for explaining an example of the operation of the magnetic disk device 1 according to the second embodiment. The series of operations shown in this figure are performed as a part of the learning operation.

[0122] The controller 30 obtains the maximum velocity in the radial direction of the magnetic head 22 based on the frequency estimated value and the amplitude estimated value obtained in the learning operation ( S301 ).

[0123] For example, the frequency f i , amplitude a i The time transition x(t) of the sinusoidal wave displacement can be expressed as the following equation (1).

[0124] x(t)=a i sin(2πf i t)…(1)

[0125] By differentiating x(t) with respect to time, the time transition v(t) of the velocity is obtained as shown in the following equation (2).

[0126] v(t)=2π i ·a i cos(2πf i t)…(2)

[0127] Therefore, the frequency f i , amplitude a i The maximum speed of the sine wave is expressed by the following formula (3).

[0128] max(v(t))=2πf i ·a i …(3)

[0129] The controller 30 can obtain the maximum speed in the radial direction of the magnetic head 22 by substituting the frequency estimation value and the amplitude estimation value into the formula (3). In addition, the controller 30 can also pre-store information recording the relationship between the frequency, amplitude, and the maximum speed in the radial direction of the magnetic head 22, and obtain the maximum speed in the radial direction of the magnetic head 22 based on the information.

[0130] Next, the controller 30 determines the stability threshold value Th based on the obtained maximum speed. stl Or write the off-track film Th WOS Then, the operation ends.

[0131] In the process of S302, the controller 30 increases the stability threshold value Th as the maximum speed is increased. stl Thus, the risk of the positioning error exceeding the write deviation piece in the writing action after the stabilization action can be reduced.

[0132] Alternatively, the faster the maximum speed is, the more the controller 30 writes the deflection track piece Th. WOS The faster the maximum speed is, the longer the distance of the supertravel is, and thus, the risk of data being destroyed in the track adjacent to the target track rises. The faster the maximum speed is, the faster the write track piece Th is. WOS The smaller it is, the less risk there is of data being destroyed in tracks adjacent to the target track due to overtravel.

[0133] (Third embodiment)

[0134] The learning value C of the stable count obtained by the learning operation of the first embodiment may sometimes become significantly large. set When an update is performed, the time required for subsequent stabilization will increase, and the seek time will increase.

[0135] In the third embodiment, the controller 30 uses a value smaller than the learning value C to set the setting value C. set At the same time, the controller 30 reduces the stability threshold Th stl .

[0136] Just use a value smaller than the learning value C to set the value C. set If the update is performed, it will not be possible to ensure that the vibration amplitude after the stabilization operation ends will reach the stabilization threshold value Th. stl the following.

[0137] For example, when the servo sampling number corresponding to 0.75 cycles of vibration is set as the set value of the stable count, the guaranteed vibration amplitude becomes Th stl *(1+sqrt(2) / 2) / 2. In addition, "*" is an operator that means a multiplication operation. "sqrt" is an operator that means a square root operation.

[0138] Fig. 9 2 is a diagram for explaining the relationship between the stable count and the guaranteed width. In this diagram, the horizontal axis represents time and the vertical axis represents position. In addition, the displacement of the magnetic head 22 vibrating at a certain frequency is plotted.

[0139] according to Fig. 9 It can be seen that when a value corresponding to a time length α times a cycle (where α is a real number greater than 0 and less than 1) is set as the setting value of the stable count, the ratio r of the guaranteed minimum width to the amplitude of the vibration is as shown in the following formula (4).

[0140] r=(1-cos(πα)) / 2…(4)

[0141] Thus, the controller 30 adjusts the set value C by using a value smaller than the learning value C. set Update and reduce the stability threshold Th stl , so that the vibration amplitude after the stable operation is guaranteed to reach the stable threshold value Th stl the following.

[0142] Hereinafter, a third embodiment will be described. In the description of the third embodiment, description of the same matters as those of the first embodiment will be omitted.

[0143] Fig.10 This is a flowchart for explaining an example of the operation of the magnetic disk device 1 according to the third embodiment. The series of operations shown in this figure are performed as a part of the learning operation.

[0144] The controller 30 determines whether the learning value C of the stable count obtained by the learning operation is greater than a predetermined threshold value (stable count threshold value Th c) is large (S401). Stable counting threshold Th c Determined in advance during design, etc.

[0145] If the determination result in S401 is YES, the controller 30 updates the set value C of the stable count with a value smaller than the learned value C of the stable count. set , so that the stable threshold Th stl is smaller than the reference value (S402). In addition, the reference value is, for example, a stable threshold value Th stl The initial setting value.

[0146] When a “No” is determined in the determination process of S401 or after the process of S402 , the operation of the magnetic disk device 1 according to the third embodiment ends.

[0147] In addition, according to Fig.10 In the example shown, the learning value C based on the stable count and the stable count threshold Th c By comparing the stable count value C, it is determined whether to reduce the stable count setting value C set and the stability threshold Th stl . Reduce the set value C of the stable count set and the stability threshold Th stl The conditions are not limited to this. In addition, the set value C of the stable count may be reduced unconditionally. set and the stability threshold Th stl .

[0148] Thus, the controller 30 updates the set value C of the stable count with a value smaller than the learning value C. set , and the set value C of the stable count set The update of the stable counting threshold Th is reduced accordingly. stl .

[0149] This ensures that the vibration amplitude after the stabilization operation ends reaches the stabilization threshold value Th. stl Below, and the seek time can be suppressed.

[0150] (Fourth embodiment)

[0151] The controller 30 accumulates the access commands received from the host 2 in a command queue allocated to the RAM 27 or the like. Furthermore, the controller 30 performs a command reordering operation when executing the plurality of access commands accumulated in the command queue. The command reordering operation is an operation of determining the execution order of the plurality of access commands independently of the order in which the commands are received from the host 2 so as to shorten the time required to execute the plurality of access commands as much as possible.

[0152] More specifically, the controller 30 stores a reordering table that records a plurality of estimated values ​​of seek time under different conditions. The conditions are, for example, seek distances, etc. The controller 30 uses the estimated values ​​under each condition recorded in the reordering table to obtain an execution order of the plurality of access commands that requires the least time. Then, the controller 30 executes the plurality of access commands in the obtained order.

[0153] As mentioned above, the seek time is based on the set value C of the stable count. set When the seek time changes (especially when the seek time becomes longer), the optimal command reordering operation cannot be performed, and the performance of the disk device is reduced.

[0154] Therefore, in the fourth embodiment, the controller 30 and the set value C of the stable count set The reordering table is updated accordingly. This suppresses the performance degradation of the magnetic disk device 1 caused by the deterioration of the efficiency of the command reordering operation.

[0155] Hereinafter, a fourth embodiment will be described. In the description of the fourth embodiment, description of matters that are the same as those of the first embodiment will be omitted.

[0156] Fig.11 This is a flowchart for explaining an example of the operation of the magnetic disk device 1 according to the fourth embodiment.

[0157] First, the controller 30 determines the set value C of the stable count. set Whether it has been updated (S501).

[0158] If the determination result in S501 is YES, the controller 30 updates the reordering table (S502). More specifically, the controller 30 updates the reordering table based on the updated set value C of the stable count. set , calculates the estimated value of the seek time. Furthermore, the controller 30 updates the old estimated value recorded in the reordering table with the new estimated value obtained by the calculation.

[0159] If it is determined as "NO" in the determination process of S501, the process of S502 is skipped.

[0160] Then, the controller 30 executes a command reordering action based on the reordering table ( S503 ), and a series of actions are completed.

[0161] Thus, the controller 30 performs command reordering based on the estimated value of the seek time. set The update of the seek time is updated accordingly.

[0162] This suppresses a decrease in the performance of the magnetic disk device 1 due to a decrease in the efficiency of the command reordering operation.

[0163] Several embodiments of the present invention have been described, but these embodiments are provided 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 scope of the invention. These embodiments and their variations are included in the scope and purpose of the invention, and are included in the invention described in the claims and their equivalents.

Claims

1. A magnetic disk device comprising a magnetic disk having a plurality of tracks, a magnetic head and a controller, the controller, moving the magnetic head to a first track which is one of the plurality of tracks, The positioning error amount of the magnetic head from the first track is obtained in a servo sampling period. After the positioning error amount is obtained to be less than the first threshold value for a first set number of times in succession, the first track is accessed using the magnetic head. estimating the frequency of residual vibration of the magnetic head caused by the movement of the magnetic head to the first track and the amplitude of the residual vibration, The first set number of times is updated based on the estimated value of the frequency of the residual vibration and the estimated value of the amplitude of the residual vibration.

2. The magnetic disk device according to claim 1, The controller updates the first set number of times with a value based on the frequency estimation value when the amplitude estimation value is larger than a second threshold value.

3. The magnetic disk device according to claim 1, The controller updates the first set number of times using a value obtained by dividing a servo sampling frequency by the frequency estimation value.

4. The magnetic disk device according to claim 2, When the residual vibration of the magnetic head includes two or more vibrations whose amplitude estimated values ​​are larger than the second threshold value, the controller updates the first set number based on the frequency estimated values ​​of each of the two or more vibrations and the difference between the frequency estimated values ​​of the two or more vibrations.

5. The magnetic disk device according to claim 4, The controller multiplies the reciprocal of the minimum value of the differences between the frequency estimation values ​​of the two or more vibrations and the frequency estimation values ​​of the two or more vibrations by a servo sampling frequency, and updates the first set number of times using a value obtained by the multiplication.

6. The magnetic disk device according to claim 1, The controller updates the first set number of times and updates the first threshold.

7. The magnetic disk device according to claim 6, The controller updates the first threshold value based on the frequency estimation value and the amplitude estimation value.

8. The magnetic disk device according to claim 1, The access is a write action, the controller, When the positioning error amount obtained during the writing operation on the first track becomes larger than a third threshold value, the writing operation is stopped. The first set number of times is updated, and the third threshold is updated based on the frequency estimation value and the amplitude estimation value.

9. The magnetic disk device according to claim 6, the controller, The first value is obtained by dividing the servo sampling frequency by the frequency estimation value. updating the first set number of times with a second value smaller than the first value, The first threshold value is decreased in accordance with the update of the first set number of times.

10. The magnetic disk device according to any one of claims 1 to 9, the controller, Perform command reordering based on estimates of seek time, The estimated value is updated in accordance with the update of the first set number of times.

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