Magnetic disk device and control method thereof

Abstract

To provide a magnetic disk device capable of accurately detecting vibrations occurring in an actuator, and a control method thereof.SOLUTION: A magnetic disk device controls driving of a motor of an actuator to seek a magnetic head from a stop position on the magnetic disk to a target position. Then, the magnetic disk device detects the acceleration speed of the seek based on the position history of the magnetic head and based on the value of the driving current of the motor, and detects the vibration generated on the actuator based on the difference in the detected acceleration speeds.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments relate to a magnetic disk device including a magnetic disk and a magnetic head, and a method for controlling the magnetic disk device. [Background technology]

[0002] A magnetic disk device equipped with a magnetic disk and a magnetic head includes an actuator that holds the magnetic head so that it can seek in the radial direction of the magnetic disk, and when writing or reading data to the magnetic disk, the magnetic head seeks (moves) in the radial direction of the magnetic disk from its previous stopping position to a target position (write position or read position) on the magnetic disk. The position of the magnetic head during a seek can be sequentially captured from the magnetic head's read data for the positioning servo pattern on the magnetic disk. When a predetermined period of time has passed while this captured position is within a specified range including the target position, it is determined that the magnetic head has reached the target position, and the seek ends. The determination of whether a certain period of time has passed while the captured position is within a specified range including the target position is called a settling determination. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 6,982,848 [Patent Document 2] Special Publication No. 1-43379 [Patent Document 3] U.S. Patent No. 7,570,445 [Patent Document 4] U.S. Patent No. 10,553,248 [Patent Document 5] U.S. Patent No. 10,217,485 Summary of the Invention [Problem to be solved by the invention]

[0004] During a magnetic head seek, vibrations may occur in the actuator due to various factors, and these vibrations are undesirable because they are transmitted to the magnetic head. An object of the embodiments is to provide a magnetic disk drive and a control method thereof that can accurately detect vibrations occurring in an actuator. [Means for solving the problem]

[0005] A magnetic disk drive according to an embodiment includes a magnetic disk, a magnetic head for writing and reading data to and from the magnetic disk, an actuator for holding the magnetic head so that it can seek in the radial direction of the magnetic disk by driving a motor, and a controller for controlling the rotation of the magnetic disk and the seeking of the magnetic head. The controller includes a seek control means for controlling the driving of the motor to cause the magnetic head to seek from a stop position on the magnetic disk to a target position, an acceleration detection means for detecting the acceleration of the seek based on the position history of the magnetic head and on the value of the drive current of the motor, and a vibration detection means for detecting vibrations occurring in the actuator based on the difference between the accelerations detected by the acceleration detection means. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram schematically illustrating the overall configuration of each embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration of a main part of a magnetic disk in each embodiment. [Figure 3] FIG. 3 is a diagram showing changes in the drive current of the motor during a seek in each embodiment, the jerk (excitation force) applied to the actuator due to the change in the drive current, and the amplitude of vibration generated in the actuator due to the jerk. [Figure 4] FIG. 4 is a block diagram showing a position acquisition section and each acceleration detection section in each embodiment. [Figure 5] FIG. 5 is a block diagram showing a modification of FIG. [Figure 6] FIG. 6 is a diagram showing both accelerations detected by the acceleration detection sections of FIGS. 4 and 5 and the difference therebetween. [Figure 7] FIG. 7 is a diagram showing the frequencies and phases of a plurality of vibrations occurring in the actuator in each embodiment, together with the drive current and jerk of the motor. [Figure 8] FIG. 8 is a diagram showing a format of a frequency table in each embodiment. [Figure 9] FIG. 9 is a flowchart showing the control of the first embodiment. [Figure 10] FIG. 10 is a diagram showing a process of settling determination in each embodiment. [Figure 11] FIG. 11 is a diagram showing a state in which a seek in the second embodiment includes a constant speed period between acceleration and deceleration, together with the drive current and jerk of the motor. [Figure 12] FIG. 12 is a diagram showing control of the acceleration drive current and deceleration drive current of the motor in the third embodiment. [Figure 13] FIG. 13 is a diagram showing control of the acceleration drive current and deceleration drive current of the motor in the fourth embodiment. [Figure 14] FIG. 14 is a diagram showing control of the acceleration drive current and deceleration drive current of the motor in the fifth embodiment. [Figure 15] FIG. 15 is a flowchart showing the control of the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] [1] First embodiment The first embodiment will be described below with reference to the drawings. 1, a magnetic disk device 1 includes a magnetic disk 2 which is a recording medium, a spindle motor 3 which rotates the magnetic disk 2, and a magnetic head 10 which writes and reads data to and from the magnetic disk 2. An actuator 20 which supports the magnetic head 10 is disposed near the magnetic disk 2.

[0008] The actuator 20 supports the magnetic head 10 so that it can seek in the radial direction of the magnetic disk 2. That is, the actuator 20 is also called an actuator block or a head stack assembly (HSA), and includes a rotating shaft 21, an arm 22 whose midsection is held by the rotating shaft 21, a voice coil motor (VCM) 23 provided at the base end of the arm 22, and a suspension member 24 provided at the tip of the arm 23 to hold the magnetic head 10. When a driving current Ivcm is supplied to the voice coil motor 23, the magnetic head 10 is rotated from a first position indicated by a dashed line to a second position indicated by a solid line. With this rotation, the magnetic head 10 seeks (moves) in the radial direction of the magnetic disk 2 along a locus T shown in the figure.

[0009] A stopper ST and a ramp mechanism RL are disposed near the actuator 20. The stopper ST limits the movement position of the magnetic head 16 on the inner periphery side of the magnetic disk 12. The ramp mechanism RL limits the movement position of the magnetic head 16 on the outer periphery side of the magnetic disk 12.

[0010] The magnetic disk device 1 includes a controller 30 which is the center of control, a head amplifier 41 which drives the magnetic head 10, a signal processing circuit 42 which is provided between the connection between this head amplifier 41 and the controller 30, a motor driver 43 which is provided between the connection between the voice coil motor 23 and the controller 30, a DRAM 44 which is a memory which stores programs etc. necessary for controlling the controller 30, a flash ROM 45 which is a memory which stores various data necessary for controlling the controller 30, and a hard disk controller (HDC) 46 which is provided between the connection between the controller 30, the hard disk controller (HDC), and an external host device 50.

[0011] The head amplifier 41 amplifies write data signals sent from the signal processing circuit 42 to the magnetic head 10, and also amplifies data signals read by the magnetic head 10. The signal processing circuit 42 appropriately processes write data signals sent from the controller 30 to the magnetic head 10 and supplies them to the head amplifier 41, and also appropriately processes read data signals amplified by the head amplifier 41 and supplies them to the controller 30. The motor driver 43 controls the drive current for the spindle motor 3 and the drive current for the voice coil motor 23 of the actuator 20 in accordance with instructions from the controller 30. The motor driver 43 also includes a current detector 43a that detects the value of the drive current Ivcm for the voice coil motor 23. The flash ROM 45 stores a frequency table 45a used in processing by a correction section 30g (described later) of the controller 30.

[0012] 2, the magnetic disk 2 has a circular shape and is coaxially fitted to the rotation shaft of the spindle motor 3, and includes a large number of tracks Tr arranged circumferentially and concentrically. Each track Tr includes a servo sector consisting of a servo pattern SB in which position data is recorded and a data area DT in which write data is stored.

[0013] The controller 30 includes, as its main functions, a position acquisition section (position acquisition means) 30a, a seek control section (seek control means) 30b, a settling determination section (determination means) 30c, an acceleration detection section (first and second acceleration detection means) 30d, a vibration detection section (vibration detection means) 30e, and a correction section (correction means) 30f.

[0014] [Location Acquisition Section 30a] The position capture section 30 a captures the position Pos of the magnetic head 10 on the magnetic disk 2 based on the position data of the servo pattern SB included in the read data of the magnetic head 10 .

[0015] [Seek Control Section 30b] The seek control section 30b controls the drive (drive current Ivcm) of the voice coil motor 23 of the actuator 20, thereby causing the magnetic head 10 to seek from the stop position on the magnetic disk 2 to the target position Pt. Specifically, the seek control section 30b controls the drive (drive current Ivcm) of the voice coil motor 23 of the actuator 20 based on the capture position Pos of the position capture section 30a, thereby causing the magnetic head 10 to seek from the stop position on the magnetic disk 2 to the target position Pt, including sequential acceleration and deceleration.

[0016] [Settling Determination Section 30c] The settling determination section 30c performs a so-called settling determination, which determines that the magnetic head 10 has reached the target position Pt when a certain period Cs has elapsed while the capture position Pos of the position capture section 30a is within a specified range that includes the target position Pt.

[0017] [Acceleration Detection Section 30d] The acceleration detection section 30d detects the seek acceleration of the magnetic head 10 based on the history of the capture position Pos of the position capture section 30a (the position history of the magnetic head 10) and also based on the value of the drive current Ivcm of the voice coil motor 23. The acceleration detected based on the history of the capture position Pos of the position capture section 30a is referred to as acceleration Apos. The acceleration detected based on the value of the drive current Ivcm of the voice coil motor 23 is referred to as acceleration Acur.

[0018] [Vibration Detection Section 30e] The vibration detection section 30e detects vibrations occurring in the actuator 20 based on the absolute value of the difference ΔAcc (=Apos-Acur) between the accelerations Apos and Acur detected by the acceleration detection section 30d. Specifically, when the difference ΔAcc between the accelerations Apos and Acur detected by the acceleration detection section 30d is equal to or greater than a threshold value, the vibration detection section 30e determines that vibrations caused by the rise of the acceleration drive current (+Ivcm) of the voice coil motor 23 are occurring in the actuator 20.

[0019] The mechanism by which vibration occurs in the actuator 20 will be described with reference to FIG. The rising edge of the acceleration drive current (+Ivcm) of the voice coil motor 23 initiates a seek of the magnetic head 10, causing the actuator 20 to accelerate (acceleration rising period). Then, at acceleration / deceleration switching timing td, the acceleration drive current (+Ivcm) falls and the deceleration drive current (-Ivcm) rises, causing the actuator 20 to decelerate (acceleration / deceleration switching period). Thereafter, the deceleration drive current (-Ivcm) falls (deceleration falling period), and the seek of the magnetic head 10 ends after a settling determination. The acceleration / deceleration switching timing td corresponds to the falling edge of the acceleration drive current (+Ivcm).

[0020] During a seek operation of the magnetic head 10, vibrations caused by the voice coil motor 23 are transmitted to the actuator 20. Because these vibrations contain multiple frequency components, vibrations are excited at frequencies for which the actuator 20 has particularly high sensitivity among its resonance characteristics. The magnitude of the excitation force caused by the voice coil motor 23 is expressed by the jerk (m / s^3, A / s). This jerk is particularly large where the drive current Ivcm of the voice coil motor 23 changes significantly. Specifically, the jerk is particularly large at the rising edge of the acceleration drive current (+Ivcm), the falling edge td of the acceleration drive current (+Ivcm), the rising edge of the deceleration drive current (-Ivcm), and the falling edge of the deceleration drive current (-Ivcm). Because the drive current Ivcm and the seek acceleration are of the same dimension, the magnitude of the rate of change of the drive current Ivcm can also be interpreted as the magnitude of the rate of change of the seek acceleration.

[0021] The amplitude of the oscillations shown in Figure 3 converges quickly, but convergence can take a long time. If convergence takes a long time, the oscillations that remain unconverged can overlap with the next oscillation and become larger. Vibrations occurring in the actuator 20 manifest as positioning errors of the magnetic head 10. If the vibrations occurring in the actuator 20 are large and do not converge until the settling determination period, causing the positioning error to exceed the specified range Sont, the settling determination is not completed and the next read / write operation cannot be started. In this case, the target sector to be read / written is passed, and a rotational delay is required until the target sector is reached again, resulting in a decrease in performance.

[0022] As shown in Figure 4, the input to the actuator 20 is the drive current Ivcm of the voice coil motor 23, and the output of the actuator 20 can be considered to be the position Pos of the magnetic head 10. If the actuator 20 were a rigid body, the acceleration of the tip of the magnetic head 10 would be simply proportional to the drive current Ivcm (because they are of the same dimension, as mentioned above). However, because the actuator 20 has a resonance characteristic, vibrations due to this resonance would be included in the position Pos of the magnetic head 10.

[0023] [Specific example of acceleration detection section 30d] Specifically, as shown in FIG. 4, the acceleration detection section 30d includes a first acceleration detection section 30d1 consisting of a differentiator 301 that detects the seek acceleration Apos by performing a second-order differential operation on the captured position Pos of the position capture section 30a, and a second acceleration detection section 30d2 that includes a calculator 302 that detects the seek acceleration Acur by multiplying the value of the drive current Ivcm of the voice coil motor 23 by a predetermined conversion coefficient Gain.

[0024] The acceleration Apos detected by the first acceleration detection section 30d1, which receives the capture position Pos of the position capture section 30a as an input, includes vibration components generated in the actuator 20 (vibration components transmitted to the magnetic head 10). The acceleration Acur detected by the second acceleration detection section 30d2, which receives only the value of the drive current Ivcm of the voice coil motor 23 as an input, does not include vibration components generated in the actuator 20. FIG. 6 shows an example of the detected accelerations Apos and Acur and the difference ΔAcc (=Apos−Acur).

[0025] The acceleration detection section 30d may have the configuration shown in Fig. 5 instead of the configuration shown in Fig. 4. The acceleration detection section 30d in Fig. 5 includes a first acceleration detection section 30d1 made up of a state estimator 311 that estimates a seek velocity Vel based on the capture position Pos of the position capture section 30a and the value of the drive current Ivcm of the voice coil motor 23, and a differentiator 312 that detects a seek acceleration Apos by performing a first-order differentiation operation on the velocity Vel estimated by the state estimator 311 at the sampling time ts, and a second acceleration detection section 30d2 made up of a calculator 302 that detects a seek acceleration Acur by multiplying the value of the drive current Ivcm of the voice coil motor 23 by a predetermined conversion coefficient Gain.

[0026] The state estimator 311, also called an observer, is a known device that can estimate the velocity of the magnetic head 10 in a future sample by inputting the values ​​of the capture position Pos of the position capture section 30a and the drive current Ivcm of the voice coil motor 23.

[0027] The acceleration Apos detected by the first acceleration detection section 30d1, which has the capture position Pos of the position capture section 30a as an input, includes vibration components occurring in the actuator 20 (vibration components transmitted to the magnetic head 10). The acceleration Acur detected by the second acceleration detection section 30d2, which has only the value of the drive current Ivcm of the voice coil motor 23 as an input, does not include vibration components occurring in the actuator 20.

[0028] The acceleration Apos can be obtained by first differentiating the estimated velocity Vel with respect to the sampling time ts, as shown in the following equation (1). Apos=dVel / dts[Track / ts 2 ]…(1) The conversion coefficient Gain for obtaining the acceleration Acur from the drive current Ivcm is expressed by the following equation (2). Gain=(BL×ts×ts) / (Tp×m)…(2)

[0029] BL is the BL constant (a coefficient resulting from the magnetic flux density of the magnet and the effective length of the wire positioned in the magnetic field) [N / A] of the voice coil motor 23. TP is the track pitch [meter / track]. m is the coil weight [kgf] of the voice coil motor 23. Therefore, the acceleration Acur can be calculated using the following equation (3). Acur = Ivcm × Gain…(3)

[0030] That is, vibration occurring in the actuator 20 can be detected based on the absolute value of the difference ΔAcc (=Apos-Acur) between the two accelerations Apos and Acur. When there is no vibration, ΔAcc is almost zero, and when vibration is occurring, the magnitude of the amplitude of the vibration is reflected in the difference ΔAcc. When ΔAcc is equal to or greater than a predetermined threshold value Thacc, it is assumed that vibration is occurring, and vibration can be detected.

[0031] [Amendment Section 30f] When the vibration detection section 30e determines that vibration is occurring due to the rising edge of the acceleration drive current (+Ivcm) of the voice coil motor 23, the correction section 30f estimates the frequency and phase of the vibration and predicts the frequency and phase of vibration that may occur in the actuator 20 due to the falling edge of the acceleration drive current (+Ivcm) of the voice coil motor 23, and corrects the falling timing td of the acceleration drive current (+Ivcm) of the voice coil motor 23 to be delayed when the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration.

[0032] In conjunction with this correction, the correction section 30f reduces (lowers) the maximum value of the acceleration drive current (+Ivcm) in the period until the fall timing td of the acceleration drive current (+Ivcm) is reached, or increases (raises) the maximum value of the deceleration drive current (-Ivcm) after the fall timing td is reached, by the amount of delay (correction amount) of the fall timing td of the acceleration drive current (+Ivcm), so that the seek distance before and after the correction is equal, that is, to avoid extending the seek distance by correcting the fall timing td of the acceleration drive current (+Ivcm) in the delayed direction.

[0033] In this correction section 30f, examples of means for estimating the frequency and phase of vibration caused by the rise of the acceleration drive current (+Ivcm) of the voice coil motor 23 include the technologies shown in U.S. Patent No. 10,553,248 (Patent Publication No. 2019-40657) and U.S. Patent No. 10,217,485 (Patent Publication No. 2020-47333).

[0034] In this embodiment, the frequency and phase of the vibration caused by the rising edge of the acceleration drive current (+Ivcm) of the voice coil motor 23 are estimated, and at least one timing (time) at which the phase of the vibration becomes a predetermined value if the vibration continues is acquired as a first time ta. The predetermined value is, for example, the phase at which the amplitude of the vibration becomes maximum or minimum.

[0035] Next, the frequency and phase of vibration that may occur in the actuator 20 due to the falling edge (at the time of acceleration / deceleration switching) of the acceleration drive current (+Ivcm) of the voice coil motor 23 are predicted, and at least one timing (time) at which the phase of the vibration becomes the above-mentioned specified value is obtained as the second time tb.

[0036] 7 shows an example of the frequency (1 / T1, 1 / T2) and phase of each of the multiple vibrations X1 and X2 generated in the actuator 20, together with the drive current Ivcm and jerk. T1 and T2 are periods.

[0037] Assuming that there is a correlation between the timing td of the fall of the acceleration drive current (+Ivcm), the timing tjmax of the peak value of the jerk that may occur due to the fall of the acceleration drive current (+Ivcm), and the timing tb at which the amplitude of the vibration that may occur due to the fall of the acceleration drive current (+Ivcm) reaches a predetermined value (zero), the timing td and the timing tb are determined to a unique value (called the delay time) Δt for each vibration frequency F.

[0038] 8 are associated in advance with a number of vibration frequencies F1, F2, ... Fn and delay times Δt1, Δt2, ... Δtn determined for each frequency, and this frequency table 45a is stored in the flash ROM 45. Then, by searching the frequency table 45a for delay times corresponding to the frequencies of vibrations that may occur due to the fall of the acceleration drive current (+Ivcm) and reading them from the frequency table 45a, and adding the read delay times to the fall timing td of the acceleration drive current (+Ivcm), it is possible to predict the timing tb at which the amplitude of vibrations that may occur due to the fall of the acceleration drive current (+Ivcm) will reach a predetermined value (zero).

[0039] For example, if the frequency of vibration that may occur due to the falling edge of the acceleration drive current (+Ivcm) is F2, the delay time Δt2 corresponding to that frequency F2 is read from the frequency table 45a by referring to the frequency table 45a, and the read delay time Δt2 is added to the falling edge timing td of the acceleration drive current (+Ivcm) to predict the timing tb (=td+Δt2) at which the amplitude of vibration that may occur due to the falling edge of the acceleration drive current (+Ivcm) will reach a predetermined value (zero). If the frequency of vibration that may occur due to the falling edge of the acceleration drive current (+Ivcm) is, for example, F3, the delay time Δt3 corresponding to that frequency F3 is read from the frequency table 45a by referring to the frequency table 45a, and the read delay time Δt3 is added to the falling edge timing td of the acceleration drive current (+Ivcm) to predict the timing tb (=td+Δt3) at which the amplitude of vibration that may occur due to the falling edge of the acceleration drive current (+Ivcm) will reach a predetermined value (zero).

[0040] The frequency F of the induced vibration changes depending on the excitation conditions. For example, the magnitude of the drive current Ivcm applied to the voice coil motor 23 changes depending on the seek distance, which changes the resonant frequency excited in the suspension 24 of the actuator 20. Therefore, it is considered that there are many frequencies F of the residual vibration. For this reason, the frequency table 45a stores as many frequencies F1, F2...Fn as possible and the delay times Δt1, Δt2...Δtn corresponding to each of the frequencies F1, F2...Fn.

[0041] When the frequency of the vibration that may occur due to the fall of the drive current for acceleration (+Ivcm) exists between any two of the frequencies F1, F2... Fn on the frequency table 45a, two delay times corresponding to each of the two frequencies are read from the frequency table 45a, and a delay time located between the two read delay times is obtained by calculation. For example, when the frequency of the vibration that may occur due to the fall of the drive current for acceleration (+Ivcm) is "F1 + fx" existing between the frequencies F1 and F2 (F1 < "F1 + fx" < F2), the delay times Δt1 and Δt2 corresponding to the frequencies F1 and F2 are read from the frequency table 45a, and a delay time "Δt1 + tx" located between the read delay times Δt1 and Δt2 is obtained by calculation (Δt1 < "Δt1 + tx" < Δt2). Similarly, when the frequency of the vibration that may occur due to the fall of the drive current for acceleration (+Ivcm) is "F2 + fy" existing between the frequencies F2 and F3 (F2 < "F2 + fy" < F3), the delay times Δt2 and Δt3 corresponding to the frequencies F2 and F3 are read from the frequency table 45a, and "Δt2 + ty" located between the read delay times Δt2 and Δt3 is obtained by calculation as the delay time (Δt2 < "Δt2 + ty" < Δt3).

[0042] [Overall Control of Controller 30] The overall control of the controller 30 will be described while referring to the flowchart of FIG. 9. When a seek of the magnetic head 10 becomes necessary (S1), the controller 30 starts a seek to move the magnetic head 10 from the stop position on the magnetic disk 2 to the target position Pt (S2). Along with this seek start, the controller 30 detects the acceleration Apos based on the history of the capture position Pos of the position capture section 30a, and detects the acceleration Acur based on the value of the drive current Ivcm of the voice coil motor 23 (S3). Then, the controller 30 obtains the difference ΔAcc (= Apos - Acur) between the two detected accelerations Apos and Acur (S4), and determines whether the absolute value of the difference ΔAcc is greater than or equal to the threshold Th Acc or not (S5). Whether the absolute value of the difference ΔAcc is greater than or equal to the threshold Th AccIn the above case (YES in S5), the controller 30 determines that vibrations caused by the rise of the acceleration drive current (+Ivcm) of the voice coil motor 23 are occurring in the actuator 20 (S6).

[0043] Following this determination, the controller 30 estimates the frequency and phase of the vibration occurring in the actuator 20, and predicts the frequency and phase of the vibration that may occur in the actuator 20 due to the falling edge of the acceleration drive current (+Ivcm) of the voice coil motor 23 (S7). Next, the controller 30 determines whether the estimated frequency and phase of the vibration match the frequency and phase of the predicted vibration (whether they are in the same phase) (S8).

[0044] In making this determination, the controller 30 defines the timing (time) at which the phase of the estimated vibration reaches a predetermined value if the vibration continues as a first time ta, defines the timing (time) at which the phase of the predicted vibration that may occur in the future reaches the predetermined value as a second time tb, defines the period that is the reciprocal of the frequency of the predicted vibration as T, and further defines a threshold value for determining whether the phases are the same as each other as Thphs. If these defined parameters satisfy the following inequality, the symbol % in the inequality indicates modulo operation. (|ta-tb|%T) <Thphs

[0045] If the above determination results are consistent (YES in S8), that is, if the estimated vibration does not converge and overlaps with the predicted vibration, but the phases of both vibrations are the same, the controller 30 determines that the vibration that has not converged may overlap with the next vibration to be generated and become larger, and corrects the upcoming falling timing td of the acceleration drive current (+Ivcm) to be delayed (S9). In this case, the controller 30 corrects the falling timing td of the acceleration drive current (+Ivcm) to be delayed so that the above-defined parameters satisfy the following inequality: (|ta-tb|%T)>Thphs

[0046] Following this correction, the controller 30 waits for the elapsed time t to reach the falling timing td (S10). When the elapsed time t reaches the timing td (YES in S10), the controller 30 executes the deceleration of the seek by falling the acceleration drive current (+Ivcm) (S11), and proceeds to the settling determination (S12).

[0047] During the period until the elapsed time t reaches the falling timing td (NO in S10), the controller 30 reduces (lowers) the maximum value of the acceleration drive current (+Ivcm) by the amount by which the falling timing td of the acceleration drive current (+Ivcm) is delayed (corrected) in order to avoid extending the seek distance by correcting the falling timing td of the acceleration drive current (+Ivcm) in the delayed direction. Alternatively, after the elapsed time t reaches the falling timing td (YES in S10), the controller 30 increases (raises) the maximum value of the deceleration drive current (-Ivcm) by the amount of delay (correction) of the falling timing td of the acceleration drive current (+Ivcm) in order to avoid extending the seek distance by correcting the falling timing td of the acceleration drive current (+Ivcm) in the delayed direction.

[0048] 10, the controller 30 starts counting the time elapsed or the number of sectors passed by a counter at time t12 when the capture position Pos of the position capture section 30a falls completely within a specified range (the range of "Pt+ΔP" to "Pt-ΔP") that includes the target position Pt, and when the count value C reaches Cs for a certain period (settling period) (time t13), the controller 30 determines that the magnetic head 10 has reached the target position Pt. The controller 30 regards this determination result as the end of the seek (YES in S13) and ends the seek.

[0049] As described above, vibrations occurring in the actuator 20 can be accurately detected. Furthermore, even if an earlier vibration remains unconverged and overlaps with a later vibration, the amplitude of the residual vibration can be prevented from becoming unnecessarily large. This allows appropriate settling determination to be made even if the residual vibration extends into the settling determination period. It is also unnecessary to take measures to extend the settling determination period Cs due to the residual vibration. It is also possible to shorten the settling period Cs. Consequently, the timing of the seek end can be made as early as possible, thereby increasing the processing speed of data read and write. Because the amplitude of the residual vibration is not unnecessarily large, the positioning accuracy of the magnetic head 10 is improved, and therefore the reliability of data read and write to the magnetic disk 2 is also improved.

[0050] [2] Second embodiment A second embodiment will be described. As shown in Figure 3, the magnitude of the residual vibration is affected by the magnitude of the first jerk generated by the rise of the acceleration drive current (+Ivcm), the magnitude of the second jerk generated when the acceleration drive current (+Ivcm) falls (switching between acceleration and deceleration), the magnitude of the third jerk generated by the fall of the deceleration drive current (-Ivcm), and the timing of the occurrence of these jerks. For example, when the phases of the multiple vibrations excited by the first, second, and third jerks are aligned, the amplitude of the residual vibration becomes large.

[0051] Taking this into consideration, in the second embodiment, the function of the seek control section 30b of the controller 30 differs from that in the first embodiment. That is, the seek control section 30b controls the drive (drive current Ivcm) of the voice coil motor 23 of the actuator 20 based on the capture position Pos of the position capture section 30a, thereby causing the magnetic head 10 to seek from a stop position on the magnetic disk 2 to a target position Pt, sequentially including acceleration, constant speed, and deceleration, as shown in FIG. 11.

[0052] The third jerk can be placed at any timing by inserting a constant speed period between acceleration and deceleration using the correction section 30f of the controller 30. By setting the constant speed period so that the phase of the vibration generated by the third jerk is not the same as the phase of the vibration generated by the first and second jerks, it is possible to suppress the amplitude of the remaining vibration. Note that, here, it is assumed that the phase of the vibration generated by the first jerk is the same as the phase of the vibration generated by the second jerk.

[0053] This section describes a method for preventing two or more vibrations from being out of phase when a constant speed period is inserted between acceleration and deceleration.Assuming that the vibration is a sine wave, there is a correlation between the timing when the drive current Ivcm starts to change, the timing when the jerk reaches its maximum value, and the timing when the phase of the vibration excited by the jerk reaches 0 [rad].

[0054] The timing when the phase of the estimated vibration reaches a predetermined value is defined as a first time ta, the timing when the phase of the predicted vibration reaches the same predetermined value is defined as a second time tb, and the period, which is the reciprocal of the frequency of the predicted vibration, is defined as T. The phase difference φ [rad] between the two vibrations is expressed by the following equation. φ=[(tb-ta) / T]×2π…(4)

[0055] As mentioned above, the amplitude of the residual vibration is maximized when the two vibrations are in phase (identical), which is the timing when [(tb-ta) / T] in the above formula (4) is an integer multiple. Therefore, if the second time tb, which is the timing when the vibration caused by the falling edge of the acceleration amount drive current (+Ivcm) reaches a predetermined phase, satisfies the following inequality, it is possible to prevent the residual amplitude from reaching a maximum value even if the estimated vibration remains. Thphs is a threshold for determining whether the phases are identical. [(tb-ta)%T]>Thphs

[0056] The correction section 30f must insert a constant-velocity period so that the seek distance before and after the correction is equal. The constant-velocity period is secured by correcting the fall timing td of the acceleration drive current (+Ivcm) in the forward direction, and the maximum value of the deceleration drive current (-Ivcm) is reduced to avoid shortening the seek distance (in this case, the rise timing of the deceleration drive current (-Ivcm) is not changed). Alternatively, the constant-velocity period is secured by correcting the rise timing of the deceleration drive current (-Ivcm) in the backward direction, and the maximum value of the deceleration drive current (-Ivcm) is increased to avoid extending the seek distance (in this case, the fall timing of the acceleration drive current (+Ivcm) is not changed). The other configurations and effects are the same as those of the first embodiment.

[0057] [3] Third embodiment A third embodiment will be described. As shown in FIG. 11, the seek control section 30b of the controller 30 causes the magnetic head 10 to seek from a stop position on the magnetic disk 2 to a target position Pt, sequentially including acceleration, constant speed, and deceleration.

[0058] When the vibration detection section 30e determines that vibration is occurring due to the rising edge of the acceleration drive current (+Ivcm) of the voice coil motor 23, the correction section 30f of the controller 30 estimates the frequency and phase of the vibration and predicts the frequency and phase of vibration that may occur in the actuator 20 due to the falling edge of the acceleration drive current (+Ivcm) of the voice coil motor 23, and in a situation where the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration, corrects the falling timing td of the acceleration drive current (+Ivcm) of the voice coil motor 23 to be delayed, as shown in Figure 12.

[0059] In conjunction with this correction, the correction section 30f increases the maximum value of the deceleration drive current (-Ivcm) by the amount (correction amount) by which the fall timing td of the acceleration drive current (+Ivcm) is delayed so that the seek distance before and after the correction is equal, that is, to avoid extending the seek distance by correcting the fall timing td of the acceleration drive current (+Ivcm) in the delayed direction. The other configurations and effects are the same as those of the first embodiment.

[0060] [4] Fourth embodiment A fourth embodiment will be described. As shown in FIG. 11, the seek control section 30b of the controller 30 causes the magnetic head 10 to seek from a stop position on the magnetic disk 2 to a target position Pt, sequentially including acceleration, constant speed, and deceleration.

[0061] When the vibration detection section 30e determines that vibration is occurring due to the rising edge of the acceleration drive current (+Ivcm) of the voice coil motor 23, the correction section 30f of the controller 30 estimates the frequency and phase of the vibration and predicts the frequency and phase of vibration that may occur in the actuator 20 due to the falling edge of the acceleration drive current (+Ivcm) of the voice coil motor 23.In a situation where the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration, the correction section 30f corrects the falling timing td of the acceleration drive current (+Ivcm) of the voice coil motor 23 to be delayed, and corrects the rising timing of the deceleration drive current (-Ivcm) of the voice coil motor 23 to be advanced, as shown in Figure 13.

[0062] The delay in deceleration caused by correcting the falling timing of the acceleration drive current (+Ivcm) to be delayed can be compensated for by correcting the rising timing of the deceleration drive current (-Ivcm) to be advanced. The other configurations and effects are the same as those of the first embodiment.

[0063] [5] Fifth embodiment A fifth embodiment will be described. As shown in FIG. 11, the seek control section 30b of the controller 30 causes the magnetic head 10 to seek from a stop position on the magnetic disk 2 to a target position Pt, sequentially including acceleration, constant speed, and deceleration.

[0064] When the vibration detection section 30e determines that vibration is occurring due to the rising edge of the acceleration drive current (+Ivcm) of the voice coil motor 23, the correction section 30f of the controller 30 estimates the frequency and phase of the vibration and predicts the frequency and phase of vibration that may occur in the actuator 20 due to the falling edge of the acceleration drive current (+Ivcm) of the voice coil motor 23, and when the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration, corrects the falling timing td of the acceleration drive current (+Ivcm) of the voice coil motor 23 in the advance direction, as shown in Figure 14.

[0065] In conjunction with this correction, the correction section 30f reduces (lowers) the maximum value of the deceleration drive current (-Ivcm) by the amount (correction amount) by which the fall timing td of the acceleration drive current (+Ivcm) is advanced so that the seek distance before and after the correction is equal, that is, to avoid shortening the seek distance by correcting the fall timing td of the acceleration drive current (+Ivcm) in the advance direction. The other configurations and effects are the same as those of the first embodiment.

[0066] [6] Sixth embodiment A sixth embodiment will be described. When the vibration detection section 30e determines that vibration is occurring due to the rising edge of the acceleration drive current (+Ivcm) of the voice coil motor 23, the correction section 30f of the controller 30 estimates the frequency and phase of the vibration and predicts the frequency and phase of vibration that may occur in the actuator 20 due to the falling edge of the acceleration drive current (+Ivcm) of the voice coil motor 23, and corrects Cs for a certain period of time of the settling determination section 30c when the frequency and phase of the estimated vibration match the frequency and phase of the predicted vibration.

[0067] The control executed by the controller 30 is shown in the flowchart of FIG. When a seek of the magnetic head 10 is required (S1), the controller 30 starts the seek of the magnetic head 10 from the stop position on the magnetic disk 2 to the target position Pt (S2). With this seek start, the controller 30 sets the fixed period Cs of the settling determination section 30c to an initial value (S2a). Next, the controller 30 detects the accelerations Apos and Acur (S3), calculates the difference ΔAcc (=Apos-Acur) between the detected accelerations Apos and Acur (S4), and determines whether the absolute value of this difference ΔAcc is greater than or equal to the threshold value Th. Acc It is determined whether the absolute value of the difference ΔAcc is equal to or greater than the threshold value Th (S5). Acc In the above case (YES in S5), the controller 30 determines that vibrations caused by the rise of the acceleration drive current (+Ivcm) of the voice coil motor 23 are occurring in the actuator 20 (S6).

[0068] Following this determination, the controller 30 estimates the frequency and phase of the vibration occurring in the actuator 20, and predicts the frequency and phase of the vibration that may occur in the actuator 20 due to the falling edge of the acceleration drive current (+Ivcm) of the voice coil motor 23 (S7). Next, the controller 30 determines whether the estimated frequency and phase of the vibration match the frequency and phase of the predicted vibration (whether they are in the same phase) (S8).

[0069] If the judgment result is a match (YES in S8), the controller 30 judges that the vibration that occurred earlier will remain without converging and will overlap with the vibration that will occur next, causing it to become larger, and corrects the fixed period Cs for settling judgment by a predetermined value in the extension direction (S9). Following this correction, the controller 30 waits for the elapsed time t to reach timing td (S10). When the elapsed time t reaches timing td (YES in S10), the controller 30 executes seek deceleration by raising the deceleration drive current (-Ivcm) (S11), and proceeds to settling determination (S12).

[0070] 10, the controller 30 starts counting the time elapsed or the number of sectors passed by a counter at time t12 when the capture position Pos of the position capture section 30a falls completely within a specified range (the range of "Pt+ΔP" to "Pt-ΔP") that includes the target position Pt, and when the count value C reaches Cs for a certain period (settling period) (time t13), the controller 30 determines that the magnetic head 10 has reached the target position Pt. The controller 30 regards this determination result as the end of the seek (YES in S13) and ends the seek.

[0071] As described above, it is possible to accurately detect vibrations occurring in the actuator 20. Furthermore, even if an earlier generated vibration remains unconverged and overlaps with a later generated vibration, increasing the amplitude of the residual vibration, and even if the residual vibration extends into the settling determination period, the settling determination period Cs is extended, so that the settling determination can be completed appropriately. Because the amplitude of the residual vibration does not increase unnecessarily, the positioning accuracy of the magnetic head 10 is improved, and the reliability of reading and writing data from and to the magnetic disk 2 is also improved.

[0072] [Variations] Furthermore, the above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied 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 within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0073] 1...magnetic disk device, 2...magnetic disk, 10...magnetic head, 20...actuator, 22...arm, 23...voice coil motor (motor), 24...suspension, 30...controller, 30a...position capture section, 30b...seek control section, 30c...settling determination section, 30d...acceleration detection section, 30e...vibration detection section, 30f...correction section, 43a...current detector.

Claims

1. A magnetic disk, a magnetic head for writing and reading data to and from the magnetic disk; an actuator that holds the magnetic head so that the magnetic head can be driven by a motor to seek in the radial direction of the magnetic disk; a controller that controls the rotation of the magnetic disk and the seek of the magnetic head; Equipped with The controller a seek control means for controlling the drive of the motor to cause the magnetic head to seek from a stop position on the magnetic disk to a target position; an acceleration detection means for detecting the seek acceleration based on the position history of the magnetic head and based on the value of the drive current of the motor; a vibration detection means for detecting vibrations occurring in the actuator based on a difference between both accelerations detected by the acceleration detection means; Including, Magnetic disk device.

2. The controller a position capture means for capturing the position of the magnetic head on the magnetic disk based on read data of the magnetic head; a determining means for determining that the magnetic head has reached the target position when a certain period of time has elapsed in a state where the capture position of the position capturing means is within a specified range that includes the target position; further comprising:

2. The magnetic disk drive according to claim 1.

3. the acceleration detection means includes first acceleration detection means for detecting the acceleration of the seek by performing a second-order differential operation on the position captured by the position capture means, and second acceleration detection means for detecting the acceleration of the seek by multiplying the value of the drive current of the motor by a predetermined conversion coefficient; 3. The magnetic disk drive according to claim 2.

4. the acceleration detection means includes first acceleration detection means for estimating a seek speed based on the capture position of the position capture means and a value of a drive current of the motor, and detecting the acceleration of the seek by performing a first-order differential operation on the estimated speed, and second acceleration detection means for detecting the acceleration of the seek by multiplying the value of the drive current of the motor by a predetermined conversion coefficient; 3. The magnetic disk drive according to claim 2.

5. the seek control means controls the drive of the motor based on the captured position of the position capture means, thereby causing the magnetic head to seek from the stop position on the magnetic disk to the target position, including sequential acceleration and deceleration; the vibration detection means determines that vibration caused by a rise in the acceleration drive current of the motor is occurring in the actuator when a difference between the two accelerations detected by the acceleration detection means is equal to or greater than a predetermined threshold value; 3. The magnetic disk drive according to claim 2.

6. The controller a correction means for estimating a frequency and a phase of the vibration when it is determined by the vibration detection means that a vibration is occurring due to a rise in the acceleration drive current of the motor, and predicting a frequency and a phase of a vibration that may occur in the actuator due to a fall in the acceleration drive current of the motor, and correcting a fall timing of the acceleration drive current of the motor when the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration; further comprising:

6. The magnetic disk drive according to claim 5.

7. the correction means corrects the falling timing of the acceleration drive current of the motor to be delayed when the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration.

7. The magnetic disk drive according to claim 6.

8. the correction means reduces the maximum value of the acceleration drive current of the motor or increases the maximum value of the deceleration drive current of the motor by an amount corresponding to the correction of the falling timing of the acceleration drive current of the motor in the delayed direction.

8. The magnetic disk drive according to claim 7.

9. the correction means corrects the falling timing of the acceleration drive current of the motor in an advance direction when the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration.

7. The magnetic disk drive according to claim 6.

10. the correction means increases the maximum value of the acceleration drive current of the motor or decreases the maximum value of the deceleration drive current of the motor by an amount corresponding to the correction of the falling timing of the acceleration drive current of the motor in the delayed direction.

10. The magnetic disk drive according to claim 9.

11. the seek control means causes the magnetic head to seek from the stop position on the magnetic disk to the target position, sequentially including acceleration, constant speed, and deceleration, based on the captured position of the position capture means; the vibration detection means determines that vibration caused by a rise in the acceleration drive current of the motor is occurring in the actuator when a difference between the two accelerations detected by the acceleration detection means is equal to or greater than a predetermined threshold value; 3. The magnetic disk drive according to claim 2.

12. The controller a correction means for estimating a frequency and phase of the vibration when it is determined by the vibration detection means that vibration is occurring due to a rise in the acceleration drive current of the motor, and predicting a frequency and phase of vibration that may occur in the actuator due to a fall in the acceleration drive current of the motor, and correcting the fall timing of the acceleration drive current of the motor to a delay in a situation where the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration; further comprising: The magnetic disk drive according to claim 11.

13. the correction means corrects the falling timing of the acceleration drive current of the motor in a delayed direction and reduces the maximum value of the acceleration drive current to the motor by the amount of the correction.

13. The magnetic disk drive according to claim 12.

14. the correction means corrects the falling timing of the acceleration drive current of the motor in a delayed direction and increases the maximum value of the deceleration drive current to the motor by the amount of the correction.

13. The magnetic disk drive according to claim 12.

15. The controller a correction means for estimating a frequency and phase of the vibration when it is determined by the vibration detection means that vibration is occurring due to a rise in the acceleration drive current of the motor, predicting a frequency and phase of vibration that may occur in the actuator due to a fall in the acceleration drive current of the motor, and correcting the fall timing of the acceleration drive current of the motor to a delay direction and correcting the rise timing of the deceleration drive current to the motor to an advance direction when the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration; further comprising: The magnetic disk drive according to claim 11.

16. The controller a correction means for estimating a frequency and phase of the vibration when it is determined by the vibration detection means that vibration is occurring due to a rise in the acceleration drive current of the motor, predicting a frequency and phase of vibration that may occur in the actuator due to a fall in the acceleration drive current of the motor, and correcting the fall timing of the acceleration drive current of the motor in an advance direction when the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration; further comprising: The magnetic disk drive according to claim 11.

17. the correction means corrects the falling timing of the acceleration drive current of the motor in an advance direction and increases the maximum value of the acceleration drive current to the motor by the amount of the correction.

17. The magnetic disk drive according to claim 16.

18. the correction means corrects the falling timing of the acceleration drive current of the motor in the leading direction and reduces the maximum value of the deceleration drive current to the motor by the amount of the correction.

17. The magnetic disk drive according to claim 16.

19. The controller a correction means for, when it is determined by the vibration detection means that vibration is occurring due to a rise in the acceleration drive current of the motor, estimating a frequency and phase of the vibration and predicting a frequency and phase of vibration that may occur in the actuator due to a fall in the acceleration drive current of the motor, and correcting the fall timing of the acceleration drive current of the motor in an advanced direction and correcting the rise timing of the deceleration drive current to the motor in a delayed direction when the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration; further comprising: The magnetic disk drive according to claim 11.

20. The controller a correction means for estimating a frequency and a phase of vibration when it is determined by the vibration detection means that vibration is occurring due to a rise in the acceleration drive current of the motor, and predicting a frequency and a phase of vibration that may occur in the actuator due to a fall in the acceleration drive current of the motor, and correcting the fixed period of the determination means when the estimated frequency and phase of the vibration match the predicted frequency and phase of the vibration; further comprising:

3. The magnetic disk drive according to claim 2.

21. A magnetic disk, a magnetic head for writing and reading data to and from the magnetic disk; an actuator that holds the magnetic head so that the magnetic head can be driven by a motor to seek in the radial direction of the magnetic disk; a controller that controls the rotation of the magnetic disk and the seek of the magnetic head; A method for controlling a magnetic disk drive comprising: By controlling the drive of the motor, the magnetic head is caused to seek from a stop position on the magnetic disk to a target position; detecting the seek acceleration based on the position history of the magnetic head and based on the value of the drive current of the motor; detecting vibrations occurring in the actuator based on a difference between the detected accelerations; A method for controlling a magnetic disk device.

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