JP3250576B2 - Disk unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass storage device for an information processing device, and more particularly to a disk device such as a magnetic disk and an optical disk.

[0002]

2. Description of the Related Art FIG. 30 shows an example of a conventional magnetic disk drive. The magnetic disk 2 is driven to rotate by a spindle motor 8. The magnetic head 10 is supported by an arm 12 and rotated by a voice coil motor (VCM) 14 to write and read data to and from the magnetic disk 2.

[0003] A servo signal reproduction processor 20 reproduces a servo signal from a read output signal of the magnetic head 10. The position signal generation unit 30 receives the servo signal and
A position signal indicating the position of is generated. The feedback control unit 40 derives a relative position error signal between the magnetic head 10 and the track 4 from the position signal and the track center signal, and controls the VC via the drive unit to minimize the position error signal.
M14 is controlled. As a result, the magnetic head 10 travels substantially following the center line of the track 4.

[0004]

The above-mentioned conventional magnetic disk drive has the following problems when the track positioning accuracy is to be higher than a predetermined accuracy (for example, 0.5 μm). .

That is, when the axis of the spindle motor 10 is displaced from the center of a concentric data track or a data track cut into a spiral, a disturbance corresponding to the eccentricity of a disk of several tens μm enters the servo system. Will be. At this time, there is a problem that the track positioning accuracy cannot be made higher than the predetermined accuracy only by the closed-loop servo gain, and the positioning accuracy is limited.

An object of the present invention is to solve the above-mentioned problems and to provide a disk device capable of positioning a head with respect to a track having a large eccentricity with little error even when the disk eccentricity is large.

[0007]

In order to solve the above-mentioned problems, the present invention considers that the operation of positioning a head on an eccentric track is a servo control following a target input that changes in one rotation cycle. Pay attention to what can be done,
A means for periodically supplying a drive input such that the control target moves in accordance with the track eccentricity as the target input from outside the closed loop is newly provided, and only the residual difference at that time is suppressed by the closed loop control system.

[0008] The first disk device of the present invention, disk servo pattern for positioning the head is recorded
Phrases and, an actuator for driving the head, feedback control head for positioning a position signal generating means for generating a position signal from the reproduction signal generated by reading the servo pattern, the head by using the position signal to a target track
A disk device having a means, storage means for storing data, when performing the positioning operation of the head by the feedback control means, stores the control amount data for one rotation of the disk in the storage means, the normal control A feed-forward control unit for adding the control amount data read from the storage unit to the control output from the feedback control unit and supplying the control output to the actuator ;
Is controlled by feedback control means.
Original control amount data when performing the head positioning operation
To the data after filtering
After inverting the series and performing further filtering
The result of reversing the time series of the data again
The data is stored in the storage means as data .

A second disk drive according to the present invention includes a disk on which a servo pattern for positioning the head is recorded, an actuator for driving the head, and a position signal based on a reproduction signal generated by the head reading the servo pattern. What is claimed is: 1. A disk drive comprising: a position signal generating means for generating a signal; and a feedback control means for positioning a head on a target track using the position signal. A storage means for storing data, and means for fixing the head at a predetermined position And the position signal data obtained by measuring the position signal for one rotation in a state where the head is fixed at a predetermined position by the head fixing means, corresponds to the reciprocal of the transfer function of the actuator-head system to be controlled. Gain or phase change or its sign inverted Advance stored in advance in the storage means as data, during normal control, and a feedforward control means for supplying to the actuator feedforward data read from the storage unit to the control output from the feedback control means adds or subtracts to feed Forward
The actuator control means is an actuator head to be controlled.
Change the inverse transfer function or the transfer function's gay and phase to
Table stored in the form of a function for
For one rotation with the head fixed at the specified position.
Table according to the amplitude of the position signal when the position signal was measured.
Gain and phase values obtained by referencing
Counts when calculating feedforward data.
Gain and phase changes given to
It is characterized in that it is configured to be a chemical amount. Book
The third disk device of the present invention is used for positioning the head.
The disk on which the servo pattern is recorded and the head
The actuator to be driven and the head
The position to generate the position signal from the reproduced signal generated by reading
The head using the position signal generation means and the position signal.
And feedback control means for positioning the
A disk device, which is a storage device for storing data.
Step, means for fixing the head in place, and head fixing
One rotation with the head fixed in place by means
Position signal data obtained by measuring the minute position signal.
On the other hand, the transmission relation of the actuator-head system to be controlled is
Gain and phase change corresponding to the reciprocal of
Feedforward from or obtained by inverting the sign
Data is stored in the storage means in advance, and normal control
At times, the control output from the feedback control means
Add the feedforward data read from the stage
Is the feed forward that is subtracted and supplied to the actuator.
And a feed-forward control means,
Position signal for one rotation with the head fixed at the specified position
Of the in-situ signal data obtained by measuring the
Apply a fixed filtering process, reverse the time series,
Apply the same processing as the specified filtering processing,
Control target for position signal data obtained by inverting the column
Is the inverse of the transfer function of the actuator-head system
Feed with corresponding gain and phase changes
Configuration to be stored in storage means as forward data
It is characterized by having been done. Fourth disc of the present invention
The device has a servo pattern for positioning the head.
Recorded disk and actuator to drive head
And the head that reads the servo pattern
Position signal generating means for generating a position signal from the raw signal;
Positioning head to target track using positioning signal
A disk drive having feedback control means.
Storage means for storing data and a head
Means for fixing the head to the position and the head by means of the head fixing means
Measurement of position signal for one rotation while fixed at a predetermined position
Is the control target for the position signal data obtained by performing
Equivalent to the inverse of the transfer function of the actuator-head system
Gain and phase change or sign
Store the inverted data as feedforward data
In advance, and feedback during normal control.
To the control output from the memory control means.
Actuate by adding or subtracting feedforward data
Feed forward control means for supplying the
The servo pattern is circular arc
Feed forward control means,
A table that stores changes in the eccentric phase with respect to the head radius position
The timing that the head reproduces the servo pattern including the
From the table according to the current track position
The phase shifted by the extracted phase change amount is
Used as a phase reference when outputting forward data.
It is characterized by being constituted as follows.

[0010]

In the first disk drive of the present invention, the data
Is stored, the head is fixed in place, and the head is
Measurement of position signal for one rotation while fixed at a predetermined position
Is the control target for the position signal data obtained by performing
Equivalent to the inverse of the transfer function of the actuator-head system
Gain and phase change or sign
The inverted data is stored as feedforward data.
Pre-stored in the stage, feedback control during normal control
Feed read from storage means to control output from means
The forward data is added or subtracted and actuated.
To the head by the feedback control means.
To the original control amount data when the positioning operation of
After filtering, the time series of the data
Is inverted and after further filtering,
The result of reversing the time series of the data again is the control amount data
Is stored in the storage means.

In the second disk device of the present invention,
The data is stored, the head is fixed in place and the head is
Of the position signal for one rotation while the
The position signal data obtained by performing the measurement is
Equivalent to the inverse of the transfer function of a certain actuator-head system
Gain or phase change or its sign
The reverse of the signal is recorded as feedforward data.
Is stored in advance in the storage means, and feedback is provided during normal control.
The control output from the control unit is added to the file read from the storage unit.
The forward-forward data is added or subtracted,
To the actuator to be controlled.
And phase of inverse transfer function or transfer function of a loaded system
Is stored in the form of a function for the head vibration amplitude.
Once with the head fixed in place
According to the amplitude of the position signal when the displacement signal was measured
Gain and phase values obtained by referring to the table
Is the reciprocal when calculating the feedforward data
And the gain given to the position signal data measured by
This is the amount of change in phase. The third disk device of the present invention
Data is stored and the head is fixed in place.
For one rotation while the head is fixed at a predetermined position.
For the position signal data obtained by measuring the position signal,
The transfer function of the actuator-head system to be controlled
Gain and phase change corresponding to the reciprocal
Or its sign is inverted to feed forward data.
Stored in the storage means in advance as a
Read from the storage means to the control output from the feedback control means.
The added feedforward data is added or subtracted.
Supplied to the actuator to fix the head in place
Measurement by measuring the position signal for one rotation
Filtering processing for the original in-situ signal data
And reverses the time series to perform the predetermined filtering.
The same process as above was performed, and the time series was inverted.
Actuator to be controlled for position signal data
Gain and phase corresponding to the reciprocal of the transfer function of the head system
Is given as feedforward data
It is stored in the storage means. The fourth disk device of the present invention
Data is stored and the head is fixed in place.
For one rotation while the head is fixed at a predetermined position.
For the position signal data obtained by measuring the position signal,
The transfer function of the actuator-head system to be controlled
Gain and phase change corresponding to the reciprocal
Or its sign is inverted to feed forward data.
Stored in the storage means in advance as a
Read from the storage means to the control output from the feedback control means.
The added feedforward data is added or subtracted.
Is supplied to the actuator and the servo pattern is
The head is formed in an arc shape in accordance with the rotation locus of the head.
A table that stores the change of the eccentric phase with respect to the radial position
Included, timing at which the head reproduces the servo pattern
From the table according to the current track position.
The phase shifted by the amount of phase change
It is used as a phase reference when outputting forward data.

[0012]

FIG. 1 shows the configuration of an embodiment in which the present invention is applied to a magnetic disk drive. The magnetic disk 2 is driven to rotate by a spindle motor 8. The magnetic head 10 is supported by an arm 12 and rotated by a voice coil motor (VCM) 14 to write and read data to and from the magnetic disk 2.

A large number of concentric or spiral tracks 4 are set on the magnetic disk 2, and coarse and precise servo patterns for positioning the head 10 are recorded on the tracks 4 in advance. The rotating shaft of the spindle motor 8 is driven at, for example, 3600 rpm.

The magnetic head 10 has a sensing width corresponding to the width of the track 4. The servo signal reproduction processing unit 20 and the position signal generation unit 30 output the relative displacement between the track 4 and the magnetic head 10 to the feedback control unit 40. The servo signal processing unit 20, the position signal generation unit 30, and the feedback control unit 40 have a known configuration, and thus will not be described in detail here. R / W amplifier 2 for amplifying a servo signal generated by head 10 reading a servo pattern
1, an EQ (equalizer) 22 for equalizing the output of the amplifier 21, and a PD for detecting the phase from the output of the EQ 23.
(Phase detector) 23, an envelope detector 24 for detecting an envelope from the output of the EQ 22, and an integrator 25 for integrating the output of the detector 24.

The position signal generator 30 decodes a track address from the output from the PD 23 of the servo signal reproduction processor 20 and outputs the decoded track address.
An A / D converter 34 that converts an output signal from the integrator 25 of the servo signal reproduction processing unit 20 into a digital signal and outputs the digital signal;
A position generator 36 for outputting a position signal indicating a relative displacement between the track 4 and the magnetic head 10 from an output signal of the converter 34.

The feedback control unit 40 calculates a difference between the position signal from the position signal generation unit 30 and the signal indicating the track center and outputs a position error signal. , And an adder 45 that adds the outputs of these components. The feedback control unit 40 includes a D / A converter 70 and a drive amplifier 80
To drive the VCM 14 to position the magnetic head 10 at the center of the track 4. The above is a known technique.

The features of the embodiment of the present invention shown in FIG. 1 are that a feed forward control unit 60 is provided, an output signal of the feed forward control unit 60 and a feedback control unit 4 are provided.
The point is that an adder 56 for adding the output signal of 0 to the D / A converter 70 is provided. The feedforward control unit 60 includes an FF (feedforward) memory 62
A switch 64 for selectively supplying an output signal of the feedback control unit 40 to the FF memory 62 and a switch 66 for selectively supplying an output signal of the FF memory 62 to the adder 56.

The above-described position generator 36, feedback control section 40, feedforward control section 60 and adder 56 can be constituted by a processor 100.

As shown in FIG. 2, the feedforward control unit 60 performs a preliminary tracking operation for positioning the magnetic head 10 on a predetermined track 4 using only the feedback control unit 40, for example, every time the power is turned on. (Step S1). In this preliminary tracking operation, the switch 66 is maintained in the off state, and the output of the feedforward control unit 60 is 0. The position signal generator 3
0 outputs a track address obtained from the reproduction signal of the coarse pattern and a linear position signal synthesized from the reproduction signal of the precision pattern. Therefore, even when the eccentricity of the track 8 is large, the tracking control is not released and is stable. Positioning is achieved.

The switch 64 is turned off during normal control, but turned on during preparatory tracking operation, and the control output 52 of the feedback control unit 40 during the positioning operation to the eccentric track 4 is equivalent to one rotation of the memory. 62 (step S2). At this time, in order to improve the signal quality, the control output for several rotations may be measured and then averaged to obtain control amount data for one rotation. It is easy to measure the control amount data for each servo sector, but the frequency can be reduced in consideration of the memory capacity and the like.

Since the magnetic head 10 receives an external force through a flexible cable or the like, a steady offset occurs in the control output when the tracking operation is performed by the feedback control unit 40. Generally, a separate correction means is provided for the external force. In this case, in order to remove the offset, data obtained by subtracting the average value of all data from each data is used as control amount data. However, when the external force received by the magnetic head 10 is small, or when the external force is substantially constant irrespective of the radial position of the head and no separate correction means is provided, this processing can be omitted.

Finally, as the control amount data stored in the memory 62, the control amount data obtained by subtracting the above average value or the data obtained by performing a filtering process on the control amount data is used (step S4). ).

The above is the description of the preliminary tracking operation. Hereinafter, the head positioning operation during normal control will be described.

At the time of normal control, the switch 66 is turned on, and the control amount data stored in the memory 66 is referred to at the same timing as that measured in the preliminary tracking operation, and is output as the feedforward control output 57. The feedforward control output 57 is added to the output 52 of the feedback control unit 40 by the adder 56, and then the D / A converter 70 and the drive amplifier 8
0 drives the VCM 14.

As a reference signal for referring to the control amount data of the memory 62 at the same timing as that measured at the time of the preliminary tracking operation, a signal obtained by reproducing the servo pattern recorded on the disk 2 by the head 10 or a reference signal
A rotation angle signal of the spindle motor 8 may be used.

With the above-described configuration and operation, the closed-loop control constituted by the position signal generator 30, the feedback controller 40, the D / A converter 70 and the VCM drive amplifier 80 reduces the steady-state positioning deviation with respect to the target track center position. Can be done.

In the embodiment of FIG. 1, the memory 62
When data obtained by performing a normal filtering process on the control amount data after subtracting the average value is stored, the phase of the control amount data on the memory 62 is shifted from the original control amount data. There is a problem that control performance deteriorates.

To solve this problem, the feedforward control unit 60 is provided with a filtering processing unit 63 for obtaining control amount data having no phase shift with respect to the original control amount data 52 as shown in FIG. What is necessary is just to transform into.
That is, as shown in FIG. 3, the filtering processing unit 63 passes the original control amount data 52 through a filter 631 (for example, a primary digital LPF), and then inverts the time series of the data by the inversion unit 632. Then, the data is again passed through the same filter 633 as the filter 631, and the time series of the data is again inverted by the inverting unit 634 to obtain control amount data to be stored in the memory 62.

The above can be realized, for example, by the following formula calculation. (i) d (k) (k = 0 ... n-1); Original control amount data 52 (ii) for i = 0 to n-1 f1 (i + 1) = F1 · f1 (i) + F2 · d (i); F1, F2: coefficients of the filter 631 (632) f1 (k): first filtering result (iii) for j = n-1 to 0; (2) and invert the calculation direction f2 (j) = F1 · f2 (j + 1) + F2 · f1 (j + 1); f2 (k): Store the second filtering result in the memory 62

However, at the time of filtering, an initial follow-up delay due to the filter time constant occurs. Therefore, data obtained by copying the original control amount data 52 and extending it for 2.3 cycles to the filter 631 (633). As input data,
What is necessary is just to take out the data of the central part where the tracking delay does not remain from the filtering result and use it as the control amount data to be stored in the memory 62.

By employing the configuration shown in FIG. 3, it is possible to obtain the filtering result data of the control amount data 52 having no phase shift not only for the fundamental wave but also for the harmonic component, so that there is no generation of a residual error following eccentricity. There is.

In the embodiment shown in FIG. 1, when the head 10 is supported by the rotating arm 12, the eccentric phase at the head position changes with respect to the rotation phase of the spindle motor 8 when the head 10 moves. If the rotation angle signal of the motor 8 is used as a reference signal for reference timing of the control amount data in the memory 62,
When the head 10 moves, there is a problem that a deviation occurs between the eccentric phase and the output phase of the addition control amount 57, and off-track remains.

In order to solve this problem, when the servo pattern 6 is formed radially on the disk 2 as shown in FIG. 4, the control data stored in the memory 62 is transmitted from the feedback control unit 40 to In this case, the timing at which the head 10 reproduces the servo pattern 6 may be used as the phase reference when the addition control amount 57 is output.

That is, it is assumed that n servo sectors in which servo patterns are formed are provided at equal intervals, and these servo sectors are numbered from 0 to (n-1). Among them, a sector unique to sector 0 is defined as sector 0, and (n-
1), the head 10 reads the servo pattern of the sector i (i = 1... N-1) at the time of normal control, and at the time of the preliminary tracking operation, the head 10 The control amount data f (i) at the time when the above servo pattern is reproduced is referred to from the memory 62 as a feedforward control output 57, and the feedforward control unit 60 is configured to add the output to the output 52 of the feedback control unit 40. I just need.

With such a configuration, when servo sectors are formed radially as shown in FIG. 4, the timing at which the same servo sector is read by the head 10 and the eccentric phase at the head position are obtained in synchronization with each other regardless of the head position. Use that thing.

That is, as shown in FIG.
Moves from the innermost circumference (ID) to the outermost circumference (OD), and the phase from the spindle rotation center changes by Δθ, the phase of the eccentricity changes by Δθ, as shown in FIG. The timing at which the same radially written servo sector is read by the head 10 also changes by the same Δθ. Therefore, it can be seen that the feedforward control output 57 should be supplied with the same phase in the same servo sector regardless of the position of the head 10.

As described above, in the embodiment of FIG. 1, when the head 10 is supported by the rotating arm 12, when the head 10 moves, the eccentric phase at the head position changes with respect to the rotation phase of the spindle motor 8. Therefore, for example, if the rotation angle signal of the spindle motor 8 is used as a reference signal for the reference timing of the control amount data in the memory 62, the difference between the eccentric phase and the output phase of the addition control amount 57 when the head 10 moves is obtained. There is a problem that the off-track remains due to the deviation in.

To solve this problem, as shown in FIG.
If the servo pattern 6 is formed in an arc shape on the disk 2 in accordance with the head rotation trajectory, a table storing the change of the eccentric phase with respect to the head radial position is added, and the control amount data on the memory 62 is stored. When adding to the control output 52 from the feedback control unit 44, the phase is shifted by the phase change amount extracted from the table according to the current track position with respect to the timing at which the head 10 reproduces the servo pattern formed in an arc shape. What is shifted may be used as a phase reference when the addition control amount 57 is output.

That is, at the timing when the head 10 reads the servo pattern of the sector i (i = 1... N-1) during the normal control, the head 10 reproduces the servo pattern on the same sector i during the preliminary tracking operation. Control amount data f (i) at the current time, the phase is shifted by the number kx of servo sectors corresponding to the eccentric phase change (from the head position at the time of the preliminary tracking operation) at the current head radius position x. f (i-
kx) is referred to from the memory 62 as the feedforward control output 57, and the output 52 of the feedback control unit 40 is output.
The feedforward control unit 60 may be configured to add

With such a configuration, as shown in FIG. 8, a table 67 in which the change of the eccentric phase with respect to the radial position of the head is stored in the feedforward control means 60 is, for example, R
This can be realized by providing the OM. FIG. 9 shows an example of the contents of the table 67 when the head position at the time of the preliminary tracking operation is set to ID (the innermost circumference). Thereby, the current head position (Track Number:
Reference is made to the aforementioned “number kx of servo sectors corresponding to eccentric phase change” in x). Of course, this relationship can be stored as a function expression.

With such a configuration, when the servo sector is formed in the same arc shape as the head locus, the head 10 moves from the innermost circumference (ID) to the outermost circumference (OB) as shown in FIG. When the phase from the spindle rotation center changes by Δθ, the phase of the eccentricity changes by Δθ, but the servo pattern is the same as the head trajectory. Therefore, as shown in FIG. The fact that the timing read by 10 does not change is used. As shown in FIG. 7, in the same servo sector, the head 10
It is understood that it is necessary to shift the phase of the feedforward control output 57 by the phase change amount Δθ from the rotation center of the head.
It can be seen that it is sufficient to store the number in the table 67 in association with Number: x).

FIGS. 10 to 18 show the effectiveness of the present invention.
The result confirmed by simulation is shown.

First, feedback control (PID control)
FIG. 10 shows a tracking waveform (for three rounds) at the time of eccentricity only in the part 40. In this example, the amount of eccentricity is 50 [μmp-p].
(± 25 [μm]). The sampling interval is 40 [μs], and one cycle is 16.8 [ms] (420 s).
amples, 59.5 Hz). Also, σ = 0.
07 [μm] noise is added as observation noise.

FIG. 10 shows that when the eccentricity of 50 [μmp-p] is suppressed only by the feedback control (PID control, loop gain at the eccentric frequency of about 43 dB), the off-track is about 0.45 [μmp-p]. ] It can be seen that there is a residual, and when looking at the control current waveform, it can be seen that vibration having an amplitude of about 10 times the sine wave component is superimposed due to the influence of position noise. Data for feed forward must be extracted from this current waveform.

Here, the filtering processing unit 6 shown in FIG.
3 shows a case where the eccentric frequency component of the control current is extracted using FIG. FIG. 11 is an enlarged vertical axis range of the control current waveform of FIG. In order to increase the signal S / N, an average of three rounds is used as an original signal for filtering. FIG. 11B shows an average of the data of the first cycle, the second cycle, and the third cycle of the waveform of FIG. 11A in the same sample. (It can be seen that the amplitude of the noise component is reduced to about 1 / (square root of 3) by averaging.)

At the time of filtering, a signal obtained by extending the averaged signal to three cycles in consideration of the initial follow-up delay of the filter output (the second and third cycles are copies of the first cycle).
Is used as an original signal for filtering (see FIG. 1).
2). This signal is converted to a digital LP of 200 [Hz] band.
The result of passing through F is the solid line in FIG. 13, which indicates that although the phase of the fundamental wave component has a delay, the noise component has been considerably removed.

Further, the result obtained by inverting the time series of this data and passing through the same filter is the solid line in FIG.
It can be seen that the phase has returned to its original state and that it has been extracted as a fairly clean sine wave.

However, the result is that the gain was reduced by passing through the LPF. To compensate for this, the reciprocal of the filter gain (for two times) at 59.5 [Hz] (1.085 in this example) is multiplied by the filtering result (FIG. 15).

FIG. 16 shows an enlarged view of the process of the filtering process. The results of the first filtering are indicated by dots, the results of the second filtering are indicated by broken lines, and the results of gain correction are indicated by solid lines. In the first filtering result, the phase is shifted and some noise components remain, but the waveform after the gain correction (solid line) has a slight distortion due to the original noise, but a nearly clear sine wave can be extracted. You can see that it is. As can be seen from the figure, the first part and the last part of the filter deviate from the original waveform due to the delay in following the filter. It is for this reason that the original signal used by the filtering is expanded first, and data of the second cycle (data after gain correction in each sample) which is not affected by this is used as feedforward data. That is, the feedforward data is as shown in FIG. 17, and at the time of tracking, a current based on the feedforward data is repeatedly added and provided for each rotation.

Next, the eccentricity suppression effect when the feedforward data obtained in the above process is used will be described. FIG. 18 shows a tracking waveform when the addition eccentricity is set to 50 [μmp-p] as in FIG. 10 and the current shown in FIG. 17 is added as feedforward data.
However, noise is not added here to separate the residual due to feedforward from the residual due to other factors. As shown in FIG.
049 [μmp-p], and the total suppression ratio together with the loop gain when feedforward is added is −60.2 [dB]. From this, it can be seen that the suppression rate against eccentricity is greatly improved by the present invention as compared with the suppression rate of only -43 dB in the conventional feedback control.

FIG. 19 shows another embodiment in which the present invention is applied to a magnetic disk drive. 19, the same portions as those in FIG. 1 are denoted by the same reference numerals. A feature of the embodiment of the present invention in FIG. 19 is that a D / A converter 70 is provided by adding a feedforward control unit 60A and an output signal of the feedforward control unit 60A and an output signal of the feedback control unit 40. Is provided with an adder 56A for supplying to the. The feedforward control unit 60A includes a switch 65 for selectively inputting a position signal from the position signal generation unit 30, and a feedforward data calculation for calculating feedforward data from a position signal input via the switch 65. And a FF (feedforward) memory 62A.

Position generator 36, feedback control unit 4
0, feed forward control unit 60A and adder 56
A can be configured by the processor 100A.

FIG. 20 shows a method in which the feedforward calculator 68 obtains feedforward data in the embodiment of FIG. In the embodiment shown in FIG.
There is means for fixing 0 to a predetermined position. Specifically, for example, a mechanical stopper is provided on the outer peripheral side, and the VCM 14
The magnetic head 10 is fixed by applying a bias current to the rotating arm 12 and pressing the rotating arm 12 against the stopper.
Using this head fixing means, the head is fixed at a predetermined position in advance, for example, every time the power is turned on (step S11).
A position signal (corresponding to the amount of eccentricity) is measured for each of the servo sectors for the rotation and stored in a memory (step S12), and an average value of the position signal data for all the servo sectors is calculated. Is subtracted from the average value (step S13), and the position signal data obtained by filtering the average value or the position signal data obtained by filtering the data corresponds to the reciprocal of the transfer function of the actuator-head system to be controlled. Gain
A phase change is given (step S14), and the sign of the obtained data is inverted (sign inversion can be omitted).
As feed-forward data for each servo sector
The data is stored in the F memory 62A (step S15).

In order to improve the signal quality, the average of the position signals for several rotations may be used as the position signal data for one rotation, and the measurement frequency of the position signal data is set for each servo sector. However, the frequency can be reduced in consideration of the memory capacity and the like.

In the following, a description will be given of a head positioning operation at the time of normal control to which feedforward control based on data calculated by the above-described method is added.

At the time of normal control, the feedforward data stored in the memory 62A is referred to at the same timing as in the above-described position signal measurement operation for one rotation, and is output as the feedforward control output 57A. After the feedforward control output 57A is added to the output 52 of the feedback control unit 40 by the adder 56A,
The drive amplifier 80 is supplied to the VCM drive amplifier 80 via the / D converter 70, and the drive amplifier 80 drives the VCM 14 accordingly.

When the sign inversion is omitted in the above-described feedforward data calculation, the adder 56A is replaced with a subtractor, and the feedforward control output 57A is output.
May be subtracted from the output 52 of the feedback control unit 40.

As a reference signal for referring to the control amount data of the memory 62A at the same timing as that measured in the preliminary tracking operation, a signal obtained by reproducing the servo pattern 6 recorded on the disk 2 by the head 10 or a reference signal For example, a rotation angle signal of the spindle motor 8 may be used.

With the above configuration, the steady-state positioning deviation with respect to the target track center position is reduced by the closed loop control composed of the position signal generator 30, the feedback controller 40, the D / A converter 70, and the VCM drive amplifier 80. The principle is as follows.

FIG. 21 is a simplified block diagram of the embodiment of the magnetic disk drive according to the present invention shown in FIG. In FIG. 21, 151 is a transfer function of a controller, 152 is a transfer function of an actuator-head system to be controlled, r
Is the center of the target track, x is the head position, d is the track eccentricity, and y is the observation position, which is the same as in the prior art. Uff is a feedforward control output newly added in the present invention.

FIG. 21 can be equivalently converted to FIG. 22.
The residual disturbance component in FIG. 21 can be expressed as the following (Equation 1).

D ′ = d + G (jω) · Uff (Equation 1)

However, when the feedforward data calculated according to the above-described method is used, the feedforward control output Uff is given by: Uff = −inverse (G (jω)) · d where G (jω) · inverse (G ( jω)) = 1, so that d ′ = 0 is obtained.

Therefore, according to the embodiment of the present invention shown in FIG. 19, the influence of the track eccentricity can be canceled and the steady positioning deviation with respect to the target track center can be reduced.

In the above-described feedforward data calculation of the embodiment of FIG. 19, when the gain and phase of the transfer function of the actuator-head system are fixed values, the loss of the bearing of the actuator changes when the vibration amplitude actually changes. By doing so, the gain and phase of the transfer function of the actuator-head system also change. Therefore, depending on the magnitude of the track eccentricity, the right side of the above (Equation 1) is not completely canceled, and there is a problem that the control performance is deteriorated.

To solve this problem, in the feedforward data calculation of the embodiment of FIG. 19, the gain and phase (| G (jω) | and p in FIG. 20) of the transfer function of the actuator-head system are fixed. Without value
What is necessary is just to make it variable according to the head vibration amplitude. Specifically, the same actuator-head system as used in the actual machine in advance (such as at the time of factory shipment) is driven by a sine wave of which amplitude is changed, and the actuator-head system using the head vibration amplitude as a parameter is used. The gain and phase (or the reciprocal thereof) of the transfer function are created and stored as a table. FIG. 23 shows an example of a table in which the gain of the transfer function of the actuator-head system is stored in the form of a function for the head vibration amplitude. FIG. 24 shows the phase of the transfer function of the actuator-head system for the function of the head vibration amplitude. 3 shows an example of a table stored in the form of a table.

Then, similarly to the method shown in FIG.
In advance, for example, every time the power is turned on, a position signal (eccentric amount) for one rotation while the head is fixed at a predetermined position is measured,
When calculating the feedforward data to be stored in the memory 62A, the values of the gain and the phase (or the reciprocal thereof) obtained by referring to the table according to the amplitude of the measured position signal data are represented by | G ( jω) | and p (or the reciprocal thereof).

By adopting such a configuration, the right side can be almost completely canceled irrespective of the actual track eccentricity (Equation 1), so that there is an advantage that the control performance is not deteriorated.

Step S13 in FIG. 20 of the embodiment in FIG.
In the case where feedforward data is calculated using data obtained by performing ordinary filtering processing on the position signal data after subtracting the average value, the extracted eccentricity amount data ( Since the phase of the filtering result data is shifted, there is a problem that a residual occurs in the cancellation result of (Equation 1) and the control performance is deteriorated. FIG. 25 shows a feedforward control unit 60A of the embodiment of FIG. 19 to solve such a problem.
Here is a modified example. In this example, a filtering processing unit 63 is provided between the switch 65 and the feedforward data calculation unit 68. The filtering processing unit 63 extracts eccentricity data having no phase shift with respect to the original position signal data supplied via the switch 65.

The filtering section 63A converts the input original position signal data into, for example, a primary digital LP
After passing through a filter 631A comprising F
The time series of the data output from 1A is inverted by the inverting unit 633A, passed again through the same filter 633A as the filter 631A, and again inverted and output by the inverting unit 634A. The feedforward data calculation unit 68 calculates feedforward data using the output result of the filtering processing unit 65 as extracted eccentricity data.

The filtering process of the processing section 63A can be realized by, for example, the following formula calculation. (i) d (k) (k = 0 ... n-1); In-situ signal data (ii) for i = 0 to n-1 d1 (i + 1) = F1 ・ d1 (i) + F2 ・ d ( i); F1, F2: coefficient of filter 631A (633A) d1 (k): first filtering result (iii) for j = n-1 to 0; invert calculation direction to (ii) d2 (j) = F1・ D2 (j + 1) + F2 ・ d1 (j + 1); d2 (k): used for calculating the second filtering result and feedforward data

However, since the initial tracking delay due to the filter time constant occurs during the filtering, the original position signal data input via the switch 65 is copied and extended to 2.3 cycles. To the filter 631A
It is preferable to take out the data of the central part where the tracking delay does not remain from the filtering result and use it as extracted eccentricity data.

With such a configuration, the filtering result data (extracted eccentricity data) of the position signal data having no phase shift can be obtained not only for the fundamental wave but also for the harmonic components, so that a residual error following the eccentricity is generated. Can not be.

In the first embodiment shown in FIG. 19, when the head 10 is supported by the rotating arm 12, the eccentric phase at the head position changes with respect to the rotation phase of the spindle motor 8 when the head 10 moves. If the rotation angle signal of the spindle motor 8 is used as a reference signal for the reference timing of the feedforward data of the memory 62A, a deviation occurs between the eccentric phase and the output phase of the feedforward data when the head 10 moves. Therefore, there is a problem that off-track remains.

In order to solve this problem, as shown in FIG. 28, when the servo pattern 6 is formed on the disk 2 in an arc shape in accordance with the head rotation trajectory, the head is provided to the feedforward control means 60A. A table storing the change of the eccentric phase with respect to the radial position is added, and the timing at which the head 10 reproduces the servo pattern 6 formed in an arc shape is changed by the phase change amount extracted from the table according to the current track position. What is shifted in phase may be used as a phase reference when outputting feedforward data on the memory 62A.

That is, it is assumed that n servo sectors in which servo patterns are formed are provided at equal intervals, and these servo sectors are numbered from 0 to (n-1). A particularly unique servo sector is defined as sector 0, and a number from (n-1) may be sequentially assigned to the sector 0). During normal control, the head 10 is moved to sector i (i = 1... n-
At the timing when the servo pattern is read in 1)), the current head radius position x with respect to the feedforward data f (i) at the same time i calculated from the position signal data with the head fixed at a predetermined position in advance. The control amount data f (i-kx) whose phase is shifted by the number kx of servo sectors corresponding to the eccentric phase change from the head fixed position at the time of the position signal measurement at the time of measuring the position signal is referred to from the memory 62A as the feedforward control output 57A, It is configured to be added to the output 52 of the control unit 40.

For this reason, as shown in FIG. 26, a table 67A storing the change of the eccentric phase with respect to the head radial position is stored in the feedforward control section 60A, for example, in the RO.
M is provided. FIG. 27 shows an example of the contents of the table 67A in the case where the head fixing position when the position signal for one rotation is measured in advance is ID (the innermost circumference). As a result, the number of servo sectors k corresponding to the eccentric phase change at the current head position (track number: x)
x "is referred to. Of course, this relationship can be stored as a function expression.

In the configuration shown in FIG. 26, as shown in FIG. 28, when the servo sector is formed in the same arc shape as the head trajectory, the head 10 moves and the phase from the spindle rotation center changes by Δθ. The phase of the eccentricity changes by Δθ, while the timing at which the same servo sector is read by the head 10 does not change because the servo pattern is the same as the head trajectory, as shown in FIG. ing.

From FIG. 29, in the same servo sector,
It is understood that it is necessary to shift the phase of the feedforward control output 57A by the amount of phase change Δθ from the rotation center of the head 10, and the feedforward control unit 60A shown in FIG. (A track number: x) and a phase change table 67A to be stored.

Although the above embodiment relates to a magnetic disk drive, the present invention is not limited to this, and can be applied to other disk drives such as an optical disk drive.

[0081]

According to the first disk drive of the present invention,
Store the data, fix the head in place, and
Measurement of position signal for one rotation while fixed at a predetermined position
Is the control target for the position signal data obtained by performing
Equivalent to the inverse of the transfer function of the actuator-head system
Gain and phase change or sign
Store the inverted data as feedforward data
In advance, and feedback during normal control.
To the control output from the memory control means.
Addition or subtraction of feed-forward data activates
And feed it back to the
To the original control amount data when the
On the other hand, after performing the filtering process,
After inverting the columns and performing further filtering
The result of reversing the time series of the data again
Since the data track is stored in the storage means, even when the data track is mounted eccentrically with respect to the rotation axis of the spindle, the suppression rate against the eccentricity can be increased, so that the off-track caused by the eccentricity can be increased. Can be reduced.

According to a second disk apparatus [0082] The present invention, de
Data, fix the head in place, and
Measurement of position signal for one rotation while fixed at the fixed position
For the position signal data obtained by performing
A gain corresponding to the reciprocal of the transfer function of the actuator-head system
And the sign of the
Storage means for storing the inverted data as feedforward data
To be stored in advance, and feedback during normal control.
The control output from the control unit is added to the file read from the storage unit.
The forward or forward data is added or subtracted and
To the actuator that is to be controlled.
The inverse transfer function or transfer function of the
A table stored in the form of a function for the head vibration amplitude
For one rotation with the head fixed in place
When the position signal is measured, the
Gain and phase values obtained by referring to
Measure reciprocal when calculating feedforward data
Gain and phase given to the
Since the amount of change was used, the data track was
Even when mounted eccentrically to the shaft,
As the suppression rate against eccentricity can be increased,
It is possible to reduce the off-track caused by this. Departure
According to the third disk device of the present application, data is stored and
Head in place and the head in place
The position obtained by measuring the position signal for one rotation in the state
To the actuator to be controlled for the
Gain and phase corresponding to the inverse of the transfer function
Changed or inverted sign
Stored in advance in the storage means as forward data.
Control during the normal control.
Feed forward data read from the storage means
Data is added or subtracted and supplied to the actuator,
Position signal for one rotation with the head fixed at the specified position
Of the in-situ signal data obtained by measuring the
Apply a fixed filtering process, reverse the time series,
Apply the same processing as the specified filtering processing,
Control target for position signal data obtained by inverting the column
Is the inverse of the transfer function of the actuator-head system
Feed with corresponding gain and phase changes
And adapted to store in the storage means as a forwarder Dodeta
The data track is skewed relative to the spindle axis of rotation.
Even if it is installed with the center,
Since the suppression rate can be increased,
Tracks can be reduced. The fourth data of the present invention
According to the disk device, data is stored and the head is moved to a predetermined position.
Once with the head fixed in place.
Position signal data obtained by measuring the position signal of the transfer
Of the actuator-head system to be controlled
Given gain and phase changes corresponding to the inverse of the function
Feedforward
Stored in the storage means in advance as
At the time of control, stored in the control output from the feedback control means
Add the feedforward data read from the
Or subtracted and supplied to the actuator,
Is formed in an arc shape in accordance with the rotation locus of the head.
The change of the eccentric phase with respect to the head radius position
A table that includes a table and allows the head to reproduce the servo pattern.
Table for the current track position
The phase shifted by the amount of phase change drawn from
Used as a phase reference when outputting feedforward data
Data track is rotated by the spindle
Even when mounted eccentrically to the shaft,
As the suppression rate against eccentricity can be increased,
It is possible to reduce the off-track caused by this.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a magnetic disk drive.

FIG. 2 is a flowchart showing a procedure for storing addition control amount data in a memory 62 during a preliminary tracking operation.

FIG. 3 is a block diagram illustrating a configuration example of a feedforward control unit in a case where a phase shift of control amount data of a memory 62 in the embodiment of FIG. 1 is eliminated.

FIG. 4 shows a disk on which a servo pattern is radially formed, and the phase of eccentricity changes by Δθ when the head 10 moves from the innermost circumference to the outermost circumference and the phase from the spindle rotation center changes by Δθ. FIG.

FIG. 5 is a diagram showing that when the phase of eccentricity changes by Δθ in the disk of FIG. 4, the timing at which the same servo sector formed radially is read by the head 10 also changes by Δθ.

FIG. 6 shows a disk in which the servo pattern is formed in an arc shape in accordance with the head rotation trajectory, and the phase of eccentricity changes by Δθ when the head 10 moves and the phase from the spindle rotation center changes by Δθ. FIG.

FIG. 7 is a diagram showing that when the phase of the eccentricity changes by Δθ in the disk of FIG. 6, the timing of reading by the heads 10 of the same servo sector formed in an arc shape in accordance with the head locus does not change.

FIG. 8 is a block diagram showing an example in which a table storing changes in the eccentric phase with respect to the head radial position is provided in the feedforward control unit 60.

FIG. 9 is a diagram showing an example of the contents stored in a table 67 for storing changes in the eccentric phase with respect to the head position shown in FIG. 8;

FIG. 10 is a waveform diagram showing an example of a tracking waveform (for three rounds) at the time of eccentricity by only the feedback control (PID control) unit 40.

FIG. 11 is a waveform diagram showing an enlarged vertical axis range of the control current waveform of FIG. 10;

FIG. 12 is a waveform diagram showing an example of an original signal for filtering of a processing unit 63 of FIG.

13 is a waveform chart showing a result of passing the original signal of FIG. 12 through a digital LPF having a band of 200 [Hz].

14 is a waveform chart showing the result of inverting the time series of the data in FIG. 13 and passing the data through the same filter.

FIG. 15 is a waveform diagram showing a result obtained by multiplying the filtering result of FIG. 14 by the reciprocal of the filter gain (for two times).

FIG. 16 shows the filtering result of FIG.
FIG. 16 is an enlarged waveform diagram showing the filtering result of FIG. 15 as a dashed line and the result of performing the gain correction of FIG. 15 as a solid line.

FIG. 17 is a waveform diagram showing data in the second cycle of FIG. 16 (data after gain correction in each sample) used as feedforward data.

18 is a waveform chart showing an example of a tracking waveform when the current shown in FIG. 17 is added as feedforward data.

FIG. 19 is a block diagram showing another embodiment in which the present invention is applied to a magnetic disk drive.

FIG. 20 is a flowchart showing a procedure for measuring a position signal for one rotation with the head fixed in advance and calculating feedforward data using the position signal (eccentricity) data.

FIG. 21 is a simplified block diagram of the embodiment of FIG.

FIG. 22 is a block diagram obtained by equivalently converting the block diagram of FIG. 21;

FIG. 23 shows an actuator in the embodiment of FIG.
FIG. 4 is a diagram illustrating an example of a table in which the gain of a transfer function of a head system is stored in the form of a function with respect to head vibration amplitude.

FIG. 24 shows an actuator in the embodiment of FIG.
FIG. 4 is a diagram illustrating an example of a table in which the phase of a transfer function of a head system is stored in the form of a function with respect to head vibration amplitude.

25 is a block diagram showing another configuration example of the feedforward control unit 60A of the embodiment in FIG. 19, in which a filtering processing unit 63A is provided between a switch 65 and a feedforward data calculation unit 68. is there.

26 is another example of the configuration of the feedforward control unit 60A in the embodiment of FIG. 19, and shows a phase change table 67A.
It is a block diagram which shows the example which provided.

FIG. 27 is a diagram illustrating an example of a change in an eccentric phase with respect to a head position, which is an example of contents stored in a phase change table 67A of FIG.

FIG. 28 shows a disk in which a servo pattern is formed on an arc in accordance with a head rotation locus, and that the phase of eccentricity changes by Δθ when the head 10 moves and the phase changes by Δθ from the spindle rotation center. FIG.

FIG. 29 is a diagram showing a change in timing at which the head 10 reproduces a servo pattern in the form of a rotation trajectory of the disk in FIG. 28.

FIG. 30 is a block diagram showing an example of a conventional magnetic disk device.

[Explanation of symbols]

 Reference Signs List 2 magnetic disk 4 track 6 servo pattern 8 spindle motor 10 magnetic head 12 arm 14 voice coil motor (VCM) 20 servo signal reproduction processing unit 30 position signal generation unit 40 feedback control unit 56, 56A adder 57, 57A feed forward control output 60, 60A Feedforward control unit 62, 62A FF memory 63, 63A Filtering processing unit 64, 65, 66 Switch 68 Feedforward data calculation unit 70 D / A converter 80 VCM drive amplifier 151 Controller transfer function 152 Control transfer function r Target Track center x Head position y Observation position d Track eccentricity

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 21/10

Claims (6)

(57) [Claims] 1. A disk on which a servo pattern for positioning a head is recorded, an actuator for driving the head, and a position signal generator for generating a position signal from a reproduction signal generated by reading the servo pattern by the head. Means and a feedback control means for positioning the head to a target track using the position signal, a storage means for storing data, and a head control operation performed by the feedback control means when the head is positioned. The control amount data for one rotation of the disk is stored in the storage means, and during normal control,
Feedforward control means for adding the control amount data read from the storage means to the control output from the feedback control means and supplying the control amount data to the actuator, wherein the feedforward control means is provided by the feedback control means The result of inverting the time series of the data after performing the filtering process on the original control amount data when performing the positioning operation of the above, and performing the above filtering process again, Is stored in the storage means as control amount data. 2. The head according to claim 2, wherein the servo pattern is formed radially, and the feed-forward control means adds the control amount data stored in the storage means to a control output from the feedback control means, and the head controls the servo control. 2. The disk device according to claim 1, wherein the timing at which the servo pattern is reproduced is used as a phase reference when the addition control amount is output. 3. The apparatus according to claim 2, further comprising a table in which the servo pattern is formed in an arc shape in accordance with a rotation locus of the head, and a table storing a change in an eccentric phase with respect to a radial position of the head. When the control amount data stored in the storage means is added to the control output from the feedback control means, the phase read from the table according to the current track position with respect to the timing at which the head reproduces the servo pattern. 2. The disk drive according to claim 1, wherein a phase shifted by a change amount is used as a phase reference at the time of output of the addition control amount. 4. A disk on which a servo pattern for positioning a head is recorded, an actuator for driving the head, and a position signal generation for generating a position signal from a reproduction signal generated by reading the servo pattern by the head. Storage means for storing data; means for fixing the head at a predetermined position; and means for storing the data in the disk drive having feedback control means for positioning the head at a target track using the position signal. A gain corresponding to the reciprocal of a transfer function of an actuator-head system to be controlled is obtained for position signal data obtained by measuring a position signal for one rotation while the head is fixed at a predetermined position by the fixing means. The one with the phase change or its sign inverted is fed forward Feed forward data read from the storage means to the control output from the feedback control means during normal control, and feeds the data to the actuator. Wherein the feedforward control means is an object to be controlled.
Of the inverse transfer function or transfer function of the actuator-head system
Gay and phase as a function of head vibration amplitude
Including the stored table, fixing the head in place
Position when the position signal for one rotation is measured
The gain obtained by referring to the above table according to the amplitude of the
Feed forward and phase values or their inverses
To the measured position signal data when calculating the
Gain and phase change
A disk device characterized by being used . 5. A servo pattern for positioning a head.
And a drive for driving the head
The actuator and the head read the servo pattern.
The position where the position signal is generated from the reproduced signal
Signal generating means, and using the position signal to look at the head.
Feedback control means for positioning the target track.
In a disk device having a storage means for storing data, and means for securing the head to a predetermined position, and fixed in position the head by the head fixing means
The position obtained by measuring the position signal for one rotation in the state
To the actuator to be controlled for the
Gain and phase corresponding to the inverse of the transfer function
Changed or inverted sign
Stored in the storage means as the forward data.
During normal control, the feedback control means
Feed-out read from the storage means to the control output of
Add or subtract word data to get the above actuator
Feed-forward control means for supplying the head to the head.
Measure the position signal for one rotation with the position fixed.
A predetermined filter is applied to the in-situ signal data obtained by
A ring process is performed, the time series is reversed, and the predetermined
Performs the same processing as the filtering process to reverse the time series.
Actuated as the control target for the position signal data
Gain corresponding to the reciprocal of the transfer function of the heater-head system
And feed-forward
Data to be stored in the storage means.
A disk device characterized by the following. 6. A servo pattern for positioning a head.
And a drive for driving the head
The actuator and the head read the servo pattern.
The position where the position signal is generated from the reproduced signal
Signal generating means, and using the position signal to look at the head.
Feedback control means for positioning the target track.
In a disk device having a storage means for storing data, and means for securing the head to a predetermined position, and fixed in position the head by the head fixing means
The position obtained by measuring the position signal for one rotation in the state
To the actuator to be controlled for the
Gain and phase corresponding to the inverse of the transfer function
Changed or inverted sign
And the over-forward data is stored in the storage hands stage
During normal control, the feedback control means
Feed-out read from the storage means to the control output of
Add or subtract word data to get the above actuator
Feed-forward control means for supplying the servo pattern to the head,
It is formed in an arc shape, and the above feedforward control
The means includes a table storing a change in eccentric phase with respect to a head radial position , and the servo pattern is stored in the table.
The current track position relative to the timing at which the head plays
Only the amount of phase change drawn from the table according to the position
Phase-shifted, feed-forward data output
That it is configured to be used as a time phase reference.
Characteristic disk device.