JP2009020969A - Magnetic disk drive and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic disk device capable of obtaining the gain of a fine-adjustable actuator while performing a reading/writing operation, and to provide its control method. <P>SOLUTION: While the magnetic disk device is generating a control signal for suppressing positional errors of a magnetic head 4 and outputs the signal to a voice coil motor 7 and an exciting signal for displacing a piezoactuator 30 is output, the gain of the piezoactuator 30 is obtained, on the basis of the displacement of the voice coil motor 7 and the exciting signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic disk device having a two-stage actuator and a control method thereof.

  In a magnetic disk device such as a hard disk, a magnetic head is supported by an arm, and a voice coil motor drives the arm to position the magnetic head on a target position of the magnetic disk, and record and reproduce information.

  In recent years, a magnetic disk device having a so-called two-stage actuator in which a fine actuator such as a piezo actuator is provided on an arm in addition to a coarse actuator such as a voice coil motor in order to further increase positioning accuracy. Proposed.

FIG. 7A shows a conventional example of a feedback control system realized in a magnetic disk device having a two-stage actuator. In this conventional example, the control signal output from the fine movement control unit Cp is input to the coarse movement control unit Cv via the gain model H of the fine movement actuator MA, so that the control system including the coarse movement actuator VCM and the fine movement actuator The control system including the MA is made non-interfering (so-called non-interference control).
US Patent No. 6898039

  By the way, in the above conventional example, in order to perform non-interference control, it is necessary to obtain the gain of the fine actuator MA and set it in the gain model H.

Patent Document 1 discloses a method for obtaining the gain of fine actuator MA with a configuration as shown in FIG. That is, in a state in which the coarse actuator VCM by the notch filter F does not respond to a particular frequency, giving a sine wave signal N _P having the particular frequency to the fine actuator MA, is periodically displaced the fine actuator MA . Then, a gain of the fine actuator MA from the amplitude ratio of the displacement and the sine wave signal N _P of the fine actuator MA.

However, in the method of Patent Document 1, for driving only the fine actuator MA by sinusoidal signals N _P, the position of the magnetic head is varied, can not be positioned at the target position. For this reason, it is necessary to interrupt other operations such as writing / reading information while obtaining the gain of the fine actuator MA. In the method of Patent Document 1, it is necessary to bother to provide a notch filter F for stopping the operation of the coarse actuator VCM.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic disk device and a control method thereof that can easily obtain the gain of a fine actuator.

  In order to solve the above problems, a method of controlling a magnetic disk device according to the present invention includes a magnetic disk, a magnetic head for reading information recorded on the magnetic disk, an arm for supporting the magnetic head, and driving the arm. Then, for a magnetic disk device comprising a coarse actuator for moving the magnetic head on the magnetic disk and a fine actuator for adjusting the position of the magnetic head with respect to the arm, the magnetic actuator is displaced. A control signal for suppressing a position error between the target position of the magnetic head and the current position based on the position information read by the magnetic head while the excitation signal is output. Generating and outputting to the coarse actuator, the displacement of the coarse actuator and the vibration Based on the item, characterized in that it comprises the steps of: determining a gain of said fine actuator.

  In one aspect of the present invention, the displacement of the coarse actuator is obtained based on a signal in a closed loop including the coarse actuator and a gain of the closed loop with respect to the signal.

  In this aspect, the signal in the closed loop may be a control signal input to the coarse actuator.

  Further, in this aspect, the method may further include a loop gain acquisition step of inputting a disturbance signal into the closed loop including the coarse actuator and obtaining the closed loop gain based on the disturbance signal and the signal in the closed loop.

  In one embodiment of the present invention, while the excitation signal is output, the magnetic head is caused to write or read user information with respect to the target position of the magnetic head.

  Next, a magnetic disk device according to the present invention includes a magnetic disk, a magnetic head for reading information recorded on the magnetic disk, an arm that supports the magnetic head, and driving the arm to move the arm on the magnetic disk. A coarse actuator that moves the magnetic head, a fine actuator that adjusts the position of the magnetic head with respect to the arm, and a control circuit, the control circuit outputting an excitation signal that displaces the fine actuator And a control signal that suppresses a position error between the target position of the magnetic head and the current position based on the position information read by the magnetic head while the excitation signal is output. A position error suppression unit that outputs to the coarse actuator, and the fine motion based on the displacement of the coarse actuator and the vibration signal. Characterized in that it comprises a gain identification section for determining the gain of the actuator, the.

  The magnetic disk device of the present invention includes a magnetic disk, a magnetic head that reads information recorded on the magnetic disk, an arm that supports the magnetic head, and the arm that drives the arm. A coarse motion actuator that moves the magnetic head, a fine motion actuator that adjusts the position of the magnetic head with respect to the arm, and a control circuit. The control circuit periodically detects the gain of the fine motion actuator. And a control signal that periodically oscillates in response to the excitation signal is output to the coarse actuator, and a target position and a current position of the magnetic head are output. The position error of is suppressed.

  According to the present invention, the position error of the magnetic head is suppressed by the coarse actuator while the vibration signal is output to the fine actuator, so that the magnetic head can be positioned at the target position. In this case, since the displacement of the fine actuator corresponds to the displacement of the coarse actuator, the gain of the fine actuator can be obtained based on the displacement of the coarse actuator and the vibration signal.

  Further, according to the present invention, since the gain of the fine motion actuator is obtained based on the displacement and the vibration signal of the coarse motion actuator, the influence of the coarse motion actuator is eliminated in gain identification as described in Patent Document 1 above. A notch filter is not required.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration example of a magnetic disk device according to an embodiment of the present invention. The magnetic disk device 1 houses a magnetic disk 2, a spindle motor 3, a magnetic head 4, a suspension arm 5, a carriage 6, a voice coil motor 7, a head amplifier 14, and a piezo actuator 30 in a housing 9.

  The magnetic disk device 1 also has a main control circuit 10, a read / write channel (R / W channel) 13 and a motor driver 17 on a substrate outside the housing 9. The main control circuit 10 includes a microprocessing unit (MPU) and a hard disk controller (HDC).

  The magnetic disk 2 is attached to the spindle motor 3 and is driven to rotate in the direction of the arrow DR in FIG. A plurality of tracks 21 arranged concentrically are formed on the magnetic disk 2. Each track 21 is provided with a servo data area 23 at a predetermined cycle along the circumferential direction. Servo data (position information) is recorded in the servo data area 23. The servo data includes track data, sector data, and burst signals for specifying the current position of the magnetic head 4 on the magnetic disk 2. In each track 21, an area sandwiched between servo data areas 23 is a user data area 25. In the user data area 25, user data (user information) is recorded.

  The magnetic head 4 is attached to the tip of the suspension arm 5 and supported on the magnetic disk 2. The suspension arm 5 is attached to a carriage 6 that is integrated with a part of the voice coil motor 7. The voice coil motor 7 is an example of a coarse actuator, and moves the magnetic head 4 in a substantially radial direction on the magnetic disk 2 by rotating the suspension arm 5.

  The piezo actuator 30 is an example of a fine actuator, and includes a piezo element. The piezo actuator 30 adjusts the position of the magnetic head 4 with respect to the suspension arm 5.

  FIG. 2 shows an exploded perspective view in which the tip of the suspension arm 5 is enlarged. The suspension arm 5 includes an arm main body 71, a flexure 72 and an FPC 73. Further, the magnetic head 4 includes a slider 81 and an element portion 82 provided on the tip side of the slider 81. The element unit 82 includes a reproducing element and a recording element, and is electrically connected to the head amplifier 14 via the FPC 73.

  The magnetic head 4 is mounted on the suspension arm 5 via a piezo actuator 30. The piezo actuator 30 moves the magnetic head 4 in the width direction of the suspension arm 5 to change the relative position between the suspension arm 5 and the magnetic head 4.

  In this embodiment, an example of a slider-driven two-stage actuator in which the magnetic head 4 is mounted on the suspension arm 5 via the piezoelectric actuator 30 is shown, but the present invention is not limited to this form. For example, the piezo actuator may be a suspension drive type two-stage actuator that drives the tip portion of the suspension arm that supports the magnetic head to move the magnetic head minutely. Further, a head drive type two-stage actuator may be used in which a piezo actuator is sandwiched between the slider 81 and the element unit 82 and the element unit 82 is directly driven to move the position of the head with respect to the slider minutely.

  Returning to the description of FIG. 1, the MPU included in the main control circuit 10 controls the entire apparatus. The MPU is positioned by reading and executing a program stored in a memory (not shown). Various controls such as control and user data recording / playback control are realized. In the present embodiment, the main control circuit 10 functions as an excitation unit, a position error suppression unit, and a gain identification unit. These functions will be described in detail later.

  In the positioning control of the magnetic head 4, the MPU specifies the current position of the magnetic head 4 based on the servo data input from the R / W channel 13, and an error indicating an error between the target position of the magnetic head 4 and the current position. A signal (PES) is generated. Then, the MPU generates a control signal for driving the voice coil motor 7 based on the PES and outputs the control signal to the motor driver 17. As a result, the magnetic head 4 is sought and positioned on the track at the target position. Further, the MPU generates a control signal for driving the piezo actuator 30 based on the PES, and outputs the control signal to the driver 17. Thereby, the magnetic head 4 is positioned with high accuracy on the track at the target position.

  The HDC included in the main control circuit 10 includes an interface controller, an error correction circuit, a buffer controller, and the like. When the HDC receives user data to be recorded on the magnetic disk 2 from an external host, the HDC outputs the user data to the R / W channel 13. Further, when the user data reproduced from the magnetic disk 2 is input from the R / W channel 13, the HDC transmits this user data to the external host. At this time, the HDC temporarily stores user data in a buffer memory (not shown) under the control of the MPU.

  When user data is input from the main control circuit 10, the R / W channel 13 modulates this user data and outputs it to the head amplifier 14. Further, when a reproduction signal reproduced from the magnetic disk 2 by the magnetic head 4 is input from the head amplifier 14, the R / W channel 13 converts this reproduction signal into digital data, demodulates it, and sends it to the main control circuit 10. Output. The R / W channel 13 extracts servo data from the reproduction signal at a predetermined sample period and outputs it to the main control circuit 10.

  When user data to be recorded on the magnetic disk 2 is input from the R / W channel 13, the head amplifier 14 outputs the user data as a recording signal to the magnetic head 4. Further, when a reproduction signal read from the magnetic disk 2 is input from the magnetic head 4, the head amplifier 14 amplifies the reproduction signal and outputs it to the R / W channel 13.

  When the driving signal for the voice coil motor 7 is input from the main control circuit 10, the motor driver 17 converts the driving signal into an analog signal, amplifies it, and outputs it to the voice coil motor 7. Further, when a control signal for the piezo actuator 30 is input from the main control circuit 10, the motor driver 17 converts the control signal into an analog signal, amplifies it, and outputs it to the piezo actuator 30.

  FIG. 3 shows a functional configuration example of the normal operation mode of the feedback control system realized in the magnetic disk device 1. The main control circuit 10 functionally has an error signal generation unit 41, a fine movement control unit 43, a gain model unit 45, a coarse movement control unit 47, and an addition unit 49 by software operation of the MPU.

  The error signal generation unit 41 is configured to detect the current position of the magnetic head 4 specified by the target position of the magnetic head 4 determined based on the recording command or the reproduction command from the external host and the servo data input from the R / W channel 13. The difference from the position is obtained, and an error signal (PES) E is generated, and this error signal E is output to the fine movement control unit 43 and the coarse movement control unit 47.

  The fine movement control unit 43 generates and outputs a control signal for driving the piezoelectric actuator 30 based on the error signal E input from the error signal generation unit 41. The transfer function of the fine movement control unit 43 has a gain corresponding to the position error, with the point where the position error represented by the error signal E becomes zero as a stable point.

  The gain model unit 45 has the same gain and phase as the piezo actuator 30, and outputs a signal corresponding to the gain when a control signal is input from the fine movement control unit 43. For this reason, the signal output from the gain model unit 45 represents the output of the piezo actuator 30.

  The adder 49 adds the error signal E input from the error signal generator 41 and the signal input from the gain model unit 45 and outputs the result to the coarse motion controller 47.

  The coarse motion control unit 47 generates and outputs a control signal for driving the voice coil motor 7 based on the signal input from the adding unit 49. The transfer function of the coarse motion control unit 47 has a stable point at a point where the position error represented by the input signal becomes zero, and has a gain corresponding to the position error.

  As described above, in this configuration example, the signal representing the output of the piezo actuator 30 is generated by the gain model unit 45 and input to the coarse motion control unit 47, and thus includes the coarse motion control unit 47 and the voice coil motor 7. The control system and the control system including the fine movement control unit 43 and the piezo actuator 30 can be made non-interfering.

  FIG. 4 shows a functional configuration example of the gain identification mode of the feedback control system realized in the magnetic disk device 1. The main control circuit 10 starts the gain identification mode at a predetermined timing and obtains the gain of the piezo actuator 30 for setting in the gain model unit 45.

  In this gain identification mode, the main control circuit 10 turns off the switch 53 provided on the electrical path from the error signal generation unit 41 to the fine movement control unit 43, thereby operating the fine movement control unit 43 and the gain model unit 45. Stop.

  As a result, the closed loop 63 including the piezo actuator 30 and the fine movement control unit 43 disappears and the closed loop 67 including the voice coil motor 7 and the coarse movement control unit 47 remains in the magnetic disk device 1.

  In this state, the main control circuit 10 outputs a vibration signal N for displacing the piezo actuator 30 to the piezo actuator 30 via the adder 51 as a vibration step (by a function as a vibration unit). The excitation signal N can be a periodic signal such as a sine wave signal.

  While the excitation signal N is being output, the main control circuit 10 generates a control signal D that suppresses the position error of the magnetic head 4 as a position error suppression step (by a function as a position error suppression unit). To the voice coil motor 7.

  Specifically, in the main control circuit 10, when the position signal Y indicating the current position of the magnetic head 4 is input, the error signal generation unit 41 determines the difference from the target position and generates the error signal E. Output to the coarse motion control unit 47. The coarse motion control unit 47 generates a control signal D for suppressing the position error of the magnetic head 4 based on the input error signal E, and outputs the control signal D to the voice coil motor 7.

  The relationship between the displacement of the voice coil motor 7 and the piezoelectric actuator 30 in the gain identification mode will be described with reference to FIG. In the figure, the positional relationship of the magnetic head 4, the voice coil motor 7, and the piezo actuator 30 with respect to the suspension arm 5 is schematically shown. A dotted line in the figure represents a target track (target position) 60 of the magnetic head 4.

  The configuration of the tip portion of the suspension arm 5 can be divided into a base portion 56 driven by the voice coil motor 7 and a support portion 55 driven by the piezo actuator 30. The element portion 82 of the magnetic head 4 is located at the tip of the support portion 55.

  Here, in the case of the slider-driven two-stage actuator of the present embodiment, the support portion 55 driven by the piezo actuator 30 corresponds to the slider 81 of the magnetic head 4. The element portion 82 is located at the tip of the slider 81 as the support portion 55 (see FIG. 2). The base 56 driven by the voice coil motor 7 corresponds to the suspension arm 5.

  In the case of a suspension-driven two-stage actuator, the support portion 55 driven by the piezo actuator 30 corresponds to the tip portion of the suspension arm that supports the magnetic head on the tip side of the piezo actuator. The base portion 56 driven by the voice coil motor 7 corresponds to a portion of the suspension arm on the rear end side with respect to the piezo actuator. In the case of the head drive type, the support portion 55 driven by the piezo actuator is the piezo actuator and the element portion 82 itself.

  As described above, since there is a structure corresponding to each of the support portion 55 and the base portion 56 in any of the slider drive type, the head drive type, and the suspension drive type, the voice coil motor 7 and the piezoelectric actuator described below. The relationship of the 30 displacements is generally established regardless of the configuration of the two-stage actuator.

Here, the displacement h _M of the piezo actuator 30 can be expressed as the displacement of the support portion 55 driven by the piezo actuator 30. The displacement h _V of the voice coil motor 7 can be represented as a displacement of the base 56 which is driven by a voice coil motor 7.

  When the excitation signal N is input, the piezo actuator 30 vibrates the support portion 55. At this time, the magnetic head 4 positioned on the target track 60 (specifically, the element portion 82 of the magnetic head 4, the same applies hereinafter) tends to move away from the target track 60 due to the vibration of the support portion 55. .

  On the other hand, the voice coil motor 7 receives the control signal D and drives the base 56 so as to suppress the position error of the magnetic head 4. That is, the voice coil motor 7 operates the base portion 56 in the direction opposite to the direction of vibration of the support portion 55 by the piezo actuator 30. As a result, the movement of the magnetic head 4 in the direction away from the target track 60 is canceled and maintained on the target track 60.

Thus, when the piezo actuator 30 is displaced to one side (displacement h _M ), the voice coil motor 7 is displaced to the other side (displacement h _V ), thereby suppressing the position error of the magnetic head 4. Therefore, in the suspension arm 5, the position of the piezo actuator 30 serving as an inflection point vibrates with respect to the target track 60, and the magnetic head 4 is maintained on the target track 60.

Here, since the support portion 55 is very short with respect to the base portion 56, the influence of rotation is negligible. In this state, the displacement h _M of the piezo actuator 30 caused by the excitation signal N is the position of the magnetic head 4. will have approximately the same size as the displacement h _V of the voice coil motor 7 is controlled so as to suppress the error.

In the present embodiment, this idea is the basic idea for obtaining the gain of the piezoelectric actuator 30. That is, when executing the above control, since the displacement h _V of displacement h _M and the voice coil motor 7 of the piezoelectric actuator 30 is substantially the same size, instead of the displacement h _M of the piezoelectric actuator 30 of the voice coil motor 7 displacement Using h _V , the gain of the piezo actuator 30 is obtained from the ratio of the displacement h _V of the voice coil motor 7 and the amplitude of the vibration signal N.

  Hereinafter, a specific method for identifying the gain of the piezo actuator 30 will be described. The main control circuit 10 shown in FIG. 4 determines the gain of the piezo actuator 30 by measuring the control signal D input to the voice coil motor 7 as a gain identification step (by a function as a gain identification unit).

  A control signal D output from the coarse motion control unit 47 and input to the voice coil motor 7 can be expressed by the following Equation 1.

G _V represents a transfer function of the coarse motion control unit 47. E represents the error signal E output from the error signal generator 41 and input to the coarse motion controller 47. P _V represents the transfer function of the voice coil motor 7. P _M represents a transfer function of the piezoelectric actuator 30. N represents an excitation signal N input to the piezo actuator 30.

Here, the time series data is measured for the control signal D and the vibration signal N, and the gain | P _M | of the piezoelectric actuator 30 at the frequency of the vibration signal N is obtained by the following formula 2 by taking the ratio of the respective amplitudes. Can be represented.

  | D (ω) | is the amplitude of the control signal D at the frequency ω. | N (ω) | is the amplitude of the excitation signal N at the frequency ω. These can be obtained using a discrete Fourier transform or the like.

  The part represented by the following mathematical formula 3 in the mathematical formula 2 represents the gain for the control signal D of the closed loop 67 including the voice coil motor 7 and the coarse motion control unit 47.

As expressed in Formula 2, the gain | P _M | of the piezo actuator 30 includes the amplitude | D (ω) | of the control signal D, the amplitude | N (ω) | of the excitation signal N, and the gain of the closed loop 67 ( It can be obtained by Equation 3). The gain | P _M | of the piezo actuator 30 obtained in this way is set in the gain model unit 45. A case where the gain of the closed loop 67 is not known will be described later.

Here, in Equation 2, the product of the amplitude | D (ω) | of the control signal D and the gain of the closed loop 67 (Equation 3 above) is the displacement h _V of the voice coil motor 7 shown in FIG. Equivalent to. Thus, the gain of the piezoelectric actuator 30 | P M _| can that is expressed by the ratio of the amplitude N of the displacement h _V and excitation signal N of the voice coil motor 7 (omega).

How to determine the displacement h _V of the voice coil motor 7 is not limited to this. For example, other signals of the closed loop 67, such as error signal E, and may be determined displacement h _V of the voice coil motor 7 by the gain of the closed loop 67 for this signal. However, since the amplitude of the error signal E becomes smaller than the amplitude of the control signal D as a result of suppressing the position error of the magnetic head 4, it is more preferable to use the control signal D.

  The position signal Y of the magnetic head 4 when the piezo actuator 30 is vibrated can be expressed by the following mathematical formula 4.

For this reason, by setting the frequency at which the gain expressed by the following formula 5 is sufficiently smaller than | P _M N | as the frequency of the excitation signal N, the magnetic head 4 is positioned well on the target track 60. can do.

Further, in order to obtain the same effect may be provided with a characteristic of the peak filter with a center frequency of the same frequency as the excitation signal N to G _V. At this time, since the gain of G _V increases at a vibration frequency, by selecting the vibration frequency of P _V is not zero, it is possible to almost zero the gain represented by Equation 5.

  According to the gain identification mode described above, the position error of the magnetic head 4 is suppressed by the operation of the voice coil motor 7 even if the excitation signal N is input to the piezo actuator 30 and the tip of the suspension arm 5 vibrates. Therefore, the main control circuit 10 can obtain the gain of the piezo actuator 30 with the magnetic head 4 positioned on the target track 60.

  Therefore, even in the middle of the gain identification mode, the main control circuit 10 obtains the gain of the piezo actuator 30 such as a recording / reproducing operation that causes the magnetic head 4 to write or read user data with respect to the target track 60. Other operations can be performed.

  The timing for starting the gain identification mode can be the timing when the main control circuit 10 is turned on, the timing when the main control circuit 10 detects the deterioration of positioning accuracy, or the like. The deterioration of the positioning accuracy may be detected when, for example, the value of the error signal E at the time of positioning is stored in a memory or the like and the average value of the error signal E exceeds a predetermined threshold.

  Here, in the present embodiment, the main control circuit 10 can perform the recording / reproducing operation even in the middle of the gain identification mode. Therefore, the threshold value for detecting the deterioration of the positioning accuracy is made relatively low, and the piezo actuator Even if the frequency for obtaining the gain of 30 is increased, the influence on the processing capability of the magnetic disk device 1 is small.

  Next, a case where the gain of the closed loop 67 represented by the above formula 3 is not known will be described. FIG. 6 shows a functional configuration example of the loop gain acquisition mode of the feedback control system realized in the magnetic disk device 1. When the gain of the closed loop 67 including the voice coil motor 7 and the coarse motion control unit 47 is not known, the main control circuit 10 starts the loop gain acquisition mode and obtains the transfer function of the closed loop 67.

  In this loop gain acquisition mode, the main control circuit 10 turns off the switch 53 provided on the electrical path from the error signal generation unit 41 to the fine movement control unit 43, thereby enabling the fine movement control unit 43, the gain model unit 45, and The operation of the piezo actuator 30 is stopped.

In this state, the main control circuit 10 outputs the disturbance signal _NE to the error signal generation unit 41 as a loop gain acquisition step (by a function as a loop gain acquisition unit). The disturbance signal N _E, as with the excitation signal N, can be a periodic signal such as a sine wave signal. Furthermore, to determine the gain of the closed loop 67 at the frequency of the excitation signal N, the disturbance signal N _E is preferably the same frequency as the vibration signal N.

Error signal generating unit 41, the disturbance signal N _E is input, and outputs an error signal E including a disturbance component due to the disturbance signal N _E. When the error signal E including a disturbance component is input, the coarse motion control unit 47 generates a control signal D corresponding to the position error represented by the error signal E and outputs the control signal D to the voice coil motor 7. That is, the control signal D outputted from the coarse control unit 47 periodically vibrates in response to the disturbance signal N _E, drives the voice coil motor 7 so as to maintain the magnetic head 4 on the target track 60.

Here, by measuring the time-series data for the disturbance signal _NE and the control signal D and taking the ratio of the respective amplitudes, the gain of the closed loop 67 can be expressed as in Equation 6 below.

| N _E (ω) | is the amplitude of the disturbance signal N _{E at} the frequency ω. This can be obtained using a discrete Fourier transform or the like.

  The gain of the closed loop 67 obtained in this way can be used when obtaining the gain of the piezo actuator 30 in the above-described gain identification mode.

  Next, differences between this embodiment and the conventional example will be described with reference to FIG. FIG. 5A shows the relationship between the displacement and the signal when obtaining the gain of the piezo actuator 30 in the magnetic disk device 1 of the present embodiment shown in FIG. On the other hand, FIG. 5B shows the relationship between the displacement and the signal when obtaining the gain of the fine actuator in the conventional magnetic disk apparatus shown in FIG. 7B.

  In this embodiment shown in FIG. 5A, the main control circuit 10 inputs an excitation signal N that periodically vibrates to the piezo actuator 30 and vibrates the support portion 55. At this time, since the main control circuit 10 drives the base 56 so as to suppress the position error of the magnetic head 4, the control signal D input to the voice coil motor 7 is a periodic vibration corresponding to the excitation signal N. Indicates. As a result, since the position error of the magnetic head 4 is suppressed, the amplitude of the error signal E is suppressed. Since the control signal D indicates a periodic vibration corresponding to the vibration signal N, the frequency of the vibration signal N is set within a frequency band in which the transfer function of the voice coil motor 7 is smaller than 1, or peak. By increasing the gain of the coarse motion control unit 47 at the frequency of the vibration signal using a filter or the like, the position error of the magnetic head 4 can be satisfactorily suppressed.

  On the other hand, in the conventional example shown in FIG. 5B, since the notch filter F is provided, the control signal input to the coarse actuator VCM has a suppressed amplitude at this frequency. VCM does not operate at this frequency. Further, in this state, since the sine wave signal N is given to the fine movement actuator MA, the fine movement actuator MA vibrates the tip of the suspension arm, and as a result, an error signal indicating the position error of the magnetic head 4 becomes a sine wave. The periodic vibration corresponding to the signal N is shown.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned form. For example, a detector for detecting the displacement h _V of the voice coil motor 7, in the gain identification mode, the amplitude of the displacement h _V and excitation signal N of the voice coil motor 7 detected | piezo from the ratio of | N (omega) The gain | P _M | of the actuator 30 may be obtained.

1 is a block diagram illustrating a configuration example of a magnetic disk device according to an embodiment of the present invention. It is the disassembled perspective view which expanded the front-end | tip part of the suspension arm. It is a block diagram showing the function structural example of the normal operation mode of the feedback control system implement | achieved in a magnetic disc apparatus. It is a block diagram showing the function structural example of the gain identification mode of the feedback control system implement | achieved in a magnetic disc apparatus. It is a figure for demonstrating the relationship of the displacement of a coarse motion actuator and a fine motion actuator. It is a block diagram showing the function structural example of the loop gain acquisition mode of the feedback control system implement | achieved in a magnetic disc apparatus. It is a block diagram which shows the structural example of the feedback control system implement | achieved in the conventional magnetic disk apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Magnetic disk apparatus, 2 Magnetic disk, 3 Spindle motor, 4 Magnetic head, 5 Suspension arm, 6 Carriage, 7 Voice coil motor (coarse actuator), 9 Case, 10 Main control circuit (Excitation part, Position error suppression) Section, gain identification section), 13 R / W channel, 14 head amplifier, 17 motor driver, 21 tracks, 23 servo data area, 25 user data area, 30 piezo actuator (fine actuator), 41 error signal generator, 43 fine movement Control unit, 45 Model unit, 47 Coarse motion control unit, 49 Adder unit, 51 Adder unit, 53 Switch, 55 Support unit, 56 Base, 60 Target track (target position), 63, 67 Closed loop, 71 Arm body, 72 Flexure 73 FPC 81 Slider 82 Element part .

Claims (7)

A magnetic disk;
A magnetic head for reading information recorded on the magnetic disk;
An arm for supporting the magnetic head;
A coarse actuator that drives the arm to move the magnetic head on the magnetic disk;
A fine actuator for adjusting the position of the magnetic head relative to the arm;
Targeting magnetic disk devices with
Outputting an excitation signal for displacing the fine actuator;
While the excitation signal is output, a control signal that suppresses a position error between the target position of the magnetic head and the current position is generated based on the position information read by the magnetic head, and is sent to the coarse actuator. Output step;
Obtaining a gain of the fine actuator based on the displacement of the coarse actuator and the excitation signal;
A control method for a magnetic disk device, comprising: A method for controlling a magnetic disk device according to claim 1, comprising:
The displacement of the coarse actuator is determined based on a signal in a closed loop including the coarse actuator and a gain of the closed loop with respect to the signal.
A method of controlling a magnetic disk device. A method of controlling a magnetic disk device according to claim 2,
The signal in the closed loop is a control signal input to the coarse actuator.
A method of controlling a magnetic disk device. A method of controlling a magnetic disk device according to claim 2,
A loop gain obtaining step of inputting a disturbance signal into a closed loop including the coarse actuator and obtaining a gain of the closed loop based on the disturbance signal and the signal in the closed loop;
A method of controlling a magnetic disk device. A method for controlling a magnetic disk device according to claim 1, comprising:
While the excitation signal is output, the magnetic head is allowed to write or read user information with respect to the target position of the magnetic head.
A method of controlling a magnetic disk device. A magnetic disk;
A magnetic head for reading information recorded on the magnetic disk;
An arm for supporting the magnetic head;
A coarse actuator that drives the arm to move the magnetic head on the magnetic disk;
A fine actuator for adjusting the position of the magnetic head relative to the arm;
A control circuit,
The control circuit includes:
An excitation unit that outputs an excitation signal for displacing the fine actuator;
While the excitation signal is output, a control signal that suppresses a position error between the target position of the magnetic head and the current position is generated based on the position information read by the magnetic head, and is sent to the coarse actuator. An output position error suppression unit;
Based on the displacement of the coarse actuator and the excitation signal, a gain identifying unit for obtaining a gain of the fine actuator;
A magnetic disk drive comprising: A magnetic disk;
A magnetic head for reading information recorded on the magnetic disk;
An arm for supporting the magnetic head;
A coarse actuator that drives the arm to move the magnetic head on the magnetic disk;
A fine actuator for adjusting the position of the magnetic head relative to the arm;
A control circuit,
When the control circuit obtains the gain of the fine actuator,
A vibration signal that periodically oscillates is output to the fine actuator, and a control signal that periodically oscillates in response to the vibration signal is output to the coarse actuator, so that the target position of the magnetic head and the current position Suppress position error with position,
A magnetic disk device characterized by the above.

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