JPH10149644A - Magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make possible correcting eccentricity and high order distortion in a track and improving reliability in recording/reproducing by providing a feedforward control circuit measuring an eccentric amount containing distortion in a magnetic disk, calculating an answering eccentric corrective amount from the distortion in a target track based on its eccentric amount and adding the eccentric corrective amount to a feedback controlled drive current at a recording/reproducing time. SOLUTION: This device is provided with a feedback controller 20 and a feedforward controller 21 for performing drive control of a voice coil motor 16. The feedforward controller 21 is constituted of a measurement circuit 22, a memory 23, a calculation circuit 24 and a compensation circuit 25. Amplitude compensation and phase compensation are performed by these circuits, and the final eccentric corrective amount, that is, a feedforward signal is generated, and is added to the signal of the feedback controller 20 to be impressed to the motor 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive having a magnetic head for recording and reproducing information on a magnetic disk.

[0002]

2. Description of the Related Art Conventionally, a hard disk drive, which is one of magnetic disk devices built in or connected to a computer or the like, is configured as shown in FIG. 5, for example. The hard disk drive 1 includes a spindle motor 1a disposed on a flat surface of a housing 2 formed of an aluminum alloy or the like, and a magnetic disk 3 that is driven to rotate at a constant angular velocity by the spindle motor 1a. I have. Further, this case 2 has an arm 4 having a vertical axis 4
It is mounted so as to be swingable around a. A voice coil 5 is attached to one end of the arm 4, and a head slider 6 on which a magnetic head is mounted is attached to the other end of the arm 4. The magnetic head is formed on the surface of the head slider 6 by, for example, a thin film technique or the like, and includes, for example, a recording head and a reproducing head. On the housing 2, the voice coil 5 is sandwiched,
Magnets 7a and 7b are attached. A voice coil motor 7 is formed by the voice coil 5 and the magnets 7a and 7b.

In such a configuration, the voice coil 5
When an electric current is supplied from the outside to the arm 4, the arm 4 rotates around the vertical axis 4a based on the force generated by the magnetic fields of the magnets 7a and 7b and the electric current flowing through the voice coil 5. Accordingly, the head slider 6 attached to the other end of the arm 4 moves substantially in the radial direction of the magnetic disk 3 as shown by the arrow X. Therefore, the magnetic head provided on the head slider 6
Seek operation is performed. Then, an information signal is magnetically recorded on the magnetic disk 3 by a signal current flowing through the recording head, and leakage of magnetic flux from the magnetization recorded on the magnetic disk 3 is detected by the reproducing head, whereby the information signal is detected. To play.

Here, a so-called discrete disk made of plastic has recently been used as the magnetic disk 3, but eccentricity may occur when the center hole is formed after molding. For this reason,
As the drive control of the voice coil motor 7, feedforward control is employed together with feedback control. The control of the voice coil motor 7 is performed, for example, as shown in FIG. That is, the voice coil motor 7 is supplied with a drive current from a control circuit (not shown) via a feedback controller 8 and is provided with a feedforward controller 9.

The feedforward controller 9 includes a measuring circuit 9b to which the driving current of the voice coil motor 7 is input via the changeover switch 9a at the time of eccentricity measurement, and a memory 9 for storing eccentricity data measured by the measuring circuit 9b.
c and a compensating circuit 9d for reading out the eccentricity data stored in the memory 9c and performing amplitude compensation and phase compensation. The measuring circuit 9b calculates the eccentricity data by measuring the time interval of the clock mark reproduction signal for a quarter cycle of the track on the magnetic disk 3 as the position error due to the eccentricity with respect to the perfect circular track, and corrects the eccentricity data. It is converted into an amount and input to the memory 9c. Also,
The compensation circuit 9d uses the index to
The eccentricity correction amount corresponding to the angular position of the magnetic disk 3 is read from the memory 9c, and the feedforward signal is generated by performing amplitude compensation and phase compensation.

[0006] The feedforward signal thus obtained is added to the output signal of the feedback controller 8 via the changeover switch 9e during recording or reproduction of the magnetic disk 3, and the feedforward signal causes the eccentricity and distortion to be reduced. The driving current corrected in this way is applied to the voice coil motor 7. Therefore, when only the feedback control is performed and the feedforward control is not performed, the displacement of the magnetic head with respect to the track of the magnetic disk 3 has a low-order sine wave shape due to the eccentricity as shown in FIG. However, due to the above-described feedforward control, a low-order sine wave component is removed from the position deviation of the magnetic head as shown in FIG. 7B.

[0007]

By the way, in the feedforward controller 9 described above, assuming that the track of the magnetic disk 3 is a perfect circle, eccentricity data for the perfect circle track is measured to reduce the amount of eccentricity. Corresponding feedforward control is performed, that is, eccentricity correction is performed by first-order sine wave approximation of eccentricity to a perfect circle. However, the track of the magnetic disk 3 is not actually a perfect circle but has a distortion of a certain frequency component. For example, higher-order distortion occurs due to distortion of a mold during plastic molding, distortion inherent in a cutting machine, and the like.

For this reason, as shown in FIGS. 7A and 7B, since the displacement of the magnetic head from the track includes higher-order track distortion, the above-described first-order sine wave approximation is used. However, the correction of the voice coil motor 7 for the higher-order track distortion is not completely performed, and it is difficult to adjust the position of the magnetic head with respect to the track of the magnetic disk with high accuracy. Therefore, strict recording and reproduction at the track center becomes impossible. For example, for a track width of about 5 μm of a magnetic disk 3 which is widely used at present, a positional deviation of about 0.3 μm from a track of a magnetic head occurs. Therefore, when the track width is reduced when the density of the disk cleat disk is increased, the ratio of the track width to the track width is increased even if the above-mentioned positional deviation of about 0.3 μm is obtained, and the reliability of recording and reproduction of the magnetic disk 3 is improved. Is reduced.

In view of the above, the present invention provides a magnetic disk device having a feedforward control function in tracking of a magnetic head capable of correcting eccentricity and higher-order distortion of tracks on a magnetic disk. The purpose is.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a magnetic disk serving as a recording medium, driving means for rotating the magnetic disk, and a magnetic disk driven by the driving means. , A head slider mounted on the tip of the actuator, and a magnetic head comprising a recording head for recording on a magnetic disk and a reproducing head for performing reproduction on the magnetic disk. A head, a drive mechanism for moving the actuator in the radial direction of the magnetic disk, and control means including a feedback control circuit and a feedforward control circuit for driving and controlling the drive mechanism, wherein the feedforward control circuit comprises: Measuring means for measuring the amount of eccentricity including distortion of Calculating means for calculating a corresponding eccentricity correction amount from distortion of the target track based on the eccentricity amount, and adding means for adding the eccentricity correction amount from the calculating means to the feedback-controlled drive current during recording / reproducing of the magnetic disk. Achieved by providing.

According to the above arrangement, when measuring the eccentricity and distortion of the track of the magnetic disk, the measuring means measures the time interval of the clock mark reproduction signal over the entire circumference of the track of the magnetic disk, for example. To measure the eccentricity of the truck. Then, at the time of recording or reproduction of the magnetic disk, the calculating means calculates an eccentricity correction amount for the track position based on the track eccentricity amount corresponding to the angular position of the magnetic disk, and calculates the eccentricity correction amount by the control means. The signal is sent to the driving means together with the output signal from the feedback control circuit. Therefore, the drive mechanism adjusts the movement of the tip of the actuator substantially in the radial direction of the magnetic disk based on signals from the feedback control circuit and the feedforward control circuit of the control means, and moves the magnetic head to the track of the magnetic disk. It will be aligned with precision.
As a result, even if the magnetic disk is a plastic discrete disk, higher-order distortion included in the track due to distortion of the mold at the time of molding or distortion inherent to the cutting machine is removed by the above-described feedforward control circuit. Will be done. Therefore, even in the case of a magnetic disk including such a high-order track distortion, high-accuracy tracking can be performed, and the reliability of recording and reproduction by the magnetic head is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiments described below are preferred specific examples of the present invention,
Although various technically preferred limitations are given, the scope of the present invention is not limited to these forms unless otherwise specified in the following description.

FIG. 1 shows an example of the configuration of a hard disk drive which is an embodiment of the magnetic disk drive of the present invention. The hard disk drive 10 includes a spindle motor 10a disposed on a flat surface of a housing 11 formed of an aluminum alloy or the like, and a magnetic disk 12 that is driven to rotate at a constant angular velocity by the spindle motor 10a. I have. Further, an arm 13 is attached to the housing 11 so as to be swingable around a vertical axis 13a. A voice coil 14 is attached to one end of the arm 13, and a head slider 15 on which a magnetic head is mounted is attached to the other end of the arm 13. The magnetic head is formed on the surface of the head slider 15 by a thin film technique or the like, and includes, for example, a recording head and a reproducing head. A magnet 16 a is provided on the housing 11 so as to sandwich the voice coil 14.
16b is attached. The voice coil motor 1 is controlled by the voice coil 14 and the magnets 16a and 16b.
6 are formed.

In such a configuration, the voice coil 1
When a current is supplied from the outside to the arm 4, the arm 13 causes the magnetic field of the magnets 16 a and 16 b and the voice coil 14
The vertical axis 1 based on the force generated by the
Rotate around 3a. As a result, the head slider 15 attached to the other end of the arm 13 moves substantially in the radial direction of the magnetic disk 12 as indicated by the arrow X. Therefore, the magnetic head provided on the head slider 15 performs a seek operation on the magnetic disk 12. Then, an information signal is magnetically recorded on the magnetic disk 12 by a signal current flowing through the recording head, and leakage of magnetic flux from the magnetization recorded on the magnetic disk 12 is detected by the reproducing head, whereby the information signal is detected. To play.

FIG. 2 shows a configuration example of a feedback controller and a feedforward controller for controlling the drive of the voice coil motor 16.
The feedback controller 20 has the same configuration as the feedback controller 8 in the conventional hard disk drive 1 shown in FIG.
6 is applied to the input signal and fed back. On the other hand, the feedforward controller 21 includes a measurement circuit 22 to which the drive current of the voice coil motor 16 is input via the changeover switch 22a at the time of measurement, and a memory 23 for storing measurement data measured by the measurement circuit 22. , Magnetic disk 12
A calculation circuit 24 for reading out the measurement data corresponding to the track position from the memory 23 and calculating the eccentricity of the track position, and compensating the amplitude and phase for the eccentricity correction amount obtained by the calculation circuit 24 And a circuit 25.

The measuring circuit 22 calculates the amount of eccentricity including distortion with respect to tracks on the magnetic disk 12
The clock mark reproduction signal time interval is measured at a plurality of locations (e.g., 32 locations) at equal angular intervals over the entire circumference of each track at three locations on the inner circumference, outer circumference, and intermediate position in the radial direction, Measurement data (eccentricity data) based on eccentricity and strain is obtained, and the eccentricity data is converted into eccentricity correction data and input to the memory 23. Also, calculation circuit 2
Reference numeral 4 reads eccentricity correction data relating to a predetermined track position of the magnetic disk 12 from the memory 23, and calculates an eccentricity correction amount including distortion corresponding to the radius of the track position.

Further, the compensation circuit 25 performs amplitude compensation and phase compensation on the eccentricity correction amount from the calculation circuit 24, and generates a final eccentricity correction amount, that is, a feedforward signal. The feedforward signal thus obtained is added to the output signal of the feedback controller 20 via the changeover switch 26 during recording or reproduction of the magnetic disk 12, and the eccentricity and the distortion are corrected by the feedforward signal. A drive current is applied to the voice coil motor 16.

The hard disk device 10 is configured as described above, and the case of measuring the eccentricity and distortion of the track of the magnetic disk 12 will be described with reference to the flowchart of FIG. First, the hard disk device 10 is mounted, and the magnetic disk 12 is driven to rotate by the spindle motor 10a (step ST1). Then, the voice coil motor 16 is driven, and the magnetic head provided at the tip of the arm 13 is loaded while flying above the surface of the magnetic disk 12 (step ST2).

In this state, the distortion of the magnetic disk 12 (Wa
viness) is measured as follows. By the drive control of the voice coil motor 16, the magnetic head is aligned with the track on the outer periphery of the magnetic disk 12, and the two changeover switches 22a and 26 are both switched to the measurement side (step ST3). . Then, the time interval of the clock mark reproduction signal on the track is measured by the measuring circuit 22 (step ST).
4). Subsequently, the measured time interval of the clock mark reproduction signal is converted into eccentricity correction amount as eccentricity data by the measuring circuit 22 (step ST5), and the eccentricity correction amount is stored in the memory 23 as outer peripheral distortion data (step ST5). ST6).

Next, by controlling the driving of the voice coil motor 16, the magnetic head is positioned with respect to the track at the radially intermediate position (hereinafter referred to as the middle circumference) of the magnetic disk 12 (step ST7). . And
The time interval of the clock mark reproduction signal on the track is measured by the measurement circuit 22 (step ST).
8). Subsequently, the measured time interval of the clock mark reproduction signal is converted by the measuring circuit 22 into an eccentricity correction amount as eccentricity data (step ST9), and this eccentricity correction amount is stored in the memory 23 as middle-peripheral distortion data (step ST9). Step ST10).

Finally, by controlling the driving of the voice coil motor 16, the magnetic head is aligned with the track on the inner circumference of the magnetic disk 12 (step ST11). Then, the time interval of the clock mark reproduction signal on the track is measured by the measurement circuit 22 (step ST12). Subsequently, the measured time interval of the clock mark reproduction signal is converted into eccentricity correction amount as eccentricity data by the measuring circuit 22 (step ST1).
3), the eccentricity correction amount is stored in the memory 23 as the inner peripheral distortion data.
(Step ST14).

From the above, the measurement of the amount of eccentricity including distortion is completed. Here, for example, if the magnetic disk 12 has 64 clock marks, up to 32nd-order distortion is measured in principle. Therefore, in the feedforward control based on the eccentric amount, the magnetic disk 1
Of the higher-order distortion of the second track, up to the 32nd-order distortion is theoretically removed. Actually, the higher-order distortion is affected by the rotation speed of the magnetic disk 12, so that the rotation speed of the magnetic disk 12 is, for example, 3600 rpm.
In this case, the distortion can be controlled up to the 32nd order. However, when the rotational speed of the magnetic disk 12 is, for example, 4200 rpm, the distortion up to the 28th order can be controlled.

At the time of recording / reproducing on the magnetic disk 12 based on the eccentricity data measured by the measuring circuit 22 and stored in the memory 23, the feedforward control is performed as shown in the flowchart of FIG. . That is, when the feedforward control is servo-on, the two changeover switches 22a and 26 are both switched to the feedforward side. And the calculation circuit 2
4, based on the radius information from the magnetic disk 12, the outer, middle and inner distortion data are read from the memory 23 (step ST 20), and the distortion data at the radius of the track is calculated by interpolation (step ST 20). Step ST2
1).

The compensation circuit 25 causes the calculation circuit 2
4 and the index pulse from the magnetic disk 12, amplitude compensation and phase compensation are performed on the distortion data (step ST22), and final distortion data (correction amount) is obtained (step ST22). Step ST
23). The distortion data is added to the feedback-controlled drive current from the feedback controller 20 via the changeover switch 26, so that the feedback-controlled and feedforward-controlled drive current is applied to the voice coil motor 16. Will be.

As described above, the amount of eccentricity including the distortion of the magnetic disk 12 is measured, and the feedforward control is performed based on the amount of eccentricity. As a result, as shown in FIG. Higher order distortion of the track can be easily removed. Therefore, even when there is a higher-order distortion in the track of the magnetic disk 12 such as a plastic discrete disk, the magnetic head is made to follow the higher-order distortion so that the magnetic head is always accurately positioned on the track center. Since they can be matched, accurate magnetic recording and reproduction can be performed.

In the above-described embodiment, each magnetic head is moved substantially in the radial direction with respect to the magnetic disk by a so-called rotary actuator to perform tracking. The present invention is not limited to this, and can be applied to a device using a linear actuator. Also, a hard disk device has been described as a magnetic disk device, but the present invention is not limited to this, and may be applied to a magnetic disk device using another disk such as a magneto-optical disk as a recording medium.

[0027]

As described above, according to the present invention,
Even in the case of a magnetic disk including higher-order track distortion, high-accuracy tracking can be performed, and the reliability of recording and reproduction by a magnetic head can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a configuration of an example of a hard disk device which is an embodiment of a magnetic disk device of the present invention.

FIG. 2 is a block diagram showing a configuration of a drive control circuit of a voice coil motor in the magnetic disk device of FIG. 1;

FIG. 3 is a control flowchart showing feedforward control in the drive control circuit of FIG. 2;

FIG. 4 is a flowchart illustrating a measurement operation of a measurement circuit in the drive control circuit of FIG. 2;

FIG. 5 is a schematic perspective view showing a configuration of an example of a hard disk device which is one of the conventional magnetic disk devices.

FIG. 6 is a block diagram showing a configuration of a drive control circuit of a voice coil motor in the magnetic disk device of FIG. 5;

FIG. 7 (A) When there is no feed forward control,
(B) When there is a conventional feed forward control,
(C) A graph showing the displacement of the magnetic head from the track when there is feedforward control according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Magnetic disk device, 10a ... Spindle motor, 11 ... Housing, 12 ... Magnetic disk, 1
3 ... arm, 14 ... voice coil, 15 ...
Floating head slider, 16 ... Voice coil motor, 20 ... Feedback controller, 21 ...
・ Feed forward controller, 22 ・ ・ ・ Measurement circuit, 22a, 26 ・ ・ ・ Changeover switch, 23 ・ ・ ・ Memory, 24 ・ ・ ・ Calculation circuit, 25 ・ ・ ・ Compensation circuit

Claims (5)

[Claims] A magnetic disk serving as a recording medium; a driving unit for driving the magnetic disk to rotate; and a tip supported to be movable substantially in a radial direction with respect to the magnetic disk rotated by the driving unit. An actuator, a head slider mounted on a tip of the actuator, a magnetic head provided on the head slider, the magnetic head including a recording head for performing recording on the magnetic disk and a reproducing head for performing reproduction, and A magnetic disk drive comprising: a drive mechanism for moving a disk in a radial direction; and a control unit including a feedback control circuit and a feedforward control circuit for driving and controlling the drive mechanism, wherein the feedforward control circuit includes Measuring means for measuring the amount of eccentricity including disk distortion; A calculating means for calculating a corresponding eccentricity correction amount from a distortion of a target track based on the eccentricity amount measured by the measuring means; and an eccentricity correction amount from the calculating means during the recording / reproducing of the magnetic disk is feedback-controlled. A magnetic disk drive comprising: an adding unit for adding a drive current. 2. The magnetic disk drive according to claim 1, wherein said measuring means measures a time interval of a clock mark reproduction signal formed on a track of said magnetic disk to obtain an eccentricity. 3. The magnetic disk drive according to claim 1, wherein the measuring unit measures the amount of eccentricity with the magnetic head fixed in a tracking direction. 4. The magnetic disk drive according to claim 1, wherein said measuring means measures the amount of eccentricity over the entire circumference of a track of said magnetic disk. 5. The magnetic disk according to claim 1, wherein the measuring means measures the eccentricity at the inner, outer and intermediate positions in the radial direction of the magnetic disk, and the calculating means interpolates and calculates the eccentricity with respect to the target track. Magnetic disk unit.