JPH01236480A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To execute a stable settling by adding a prescribed brake to the moving speed of a magnetic head with a brake signal when the magnetic head arrives in the prescribed range of a target position track and is switched from a speed control to a position control. CONSTITUTION:A control circuit 20, when the distance up to the target position track calculated by a detecting circuit 18 based on a peak level value supplied discretely for one sampling period is within a 1/2 track, interrupts the speed control and stops a speed control signal. Further, before switching is executed to the position control, a brake signal is generated based on a correct distance and a moving speed up to the then target position track and the brake signal is supplied through a D/A converter 21 to an actuator driving circuit 22. Consequently, the brake can be applied to the movement of a magnetic head 11 in accordance with the correct distance up to the target position track at this time and the moving speed of the magnetic head 11 at this time. Thus, the stable settling can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic disk device that performs digital servo access control.

(Prior Art) Magnetic disk devices have been known that record various information signals as spiral or concentric tracks on a rigid disk housed in the main body of the device. Information signals are recorded and reproduced by a magnetic head that moves in the radial direction of the surface of a magnetic disk that rotates at high speed.

Further, in this magnetic disk device, access control consisting of speed control and position control is applied to the magnetic head so that it accurately on-tracks a predetermined track in a short time.

As a magnetic disk device that performs such access control, there is a patent application filed in 1986-8 filed earlier by the applicant of the present application.
The one described in No. 2212 is known.

That is, as shown in FIG. 6, the magnetic head 1 is placed on a rack 4 that meshes with a pinion 3 attached to the rotating shaft of an access motor 2, and by driving the access motor 2 to rotate as appropriate, the magnetic head 1 can be rotated. is moved in the radial direction of the disk D.

Further, a disk 5 is concentrically attached to the rotating shaft of the access motor 2, and the outer periphery of the disk 5 has Sf!
and N@ are alternately magnetized at a predetermined fine pitch.

Furthermore, an MR element (magnetoresistive effect element) 6 is disposed near the outer periphery of the disk 5 and faces the magnetized portion in close proximity, and as the access motor 2 rotates, this MR element The element 6 is designed to output a sinusoidal detection output as shown in FIG. 7, in which the zero cross point corresponds to the track center.

The conventional magnetic disk drive uses the above-mentioned detection output to determine the absolute position 1 of the magnetic head 1 in the disk radial direction, the distance (number of tracks) between the current position track and the target position track, or the distance of the magnetic head 1. The moving speed is sequentially detected, and based on these detection results, speed control is performed to move the magnetic head at high speed from the current position to a predetermined track position, and then the speed control is switched to position control to move the magnetic head. Positioning is performed so that the target position is accurately on-track.

(Problem to be Solved by the Invention) By the way, in conventional magnetic disk drives, switching from speed control to position control during access control is generally performed when the magnetic head 1 is lubricated from the target position track center.
This is performed when the position 1 is reached, which is 2 tracks away.

The fact that the magnetic helad 1 has reached the switching point in this way is detected based on the detection output.

However, in conventional magnetic disk drives, the zero-crossing point of the detection output may no longer correspond to the track center of each track due to the occurrence of thermal off-track due to changes in environmental temperature.

For this reason, it becomes impossible to accurately detect the switching timing from speed control to position control as described above, and it becomes impossible to accurately switch from speed control to position control.

If accurate switching is not possible in this way, in the conventional magnetic disk drive described above, the settling time for positioning the magnetic head l to the track center of the target position track becomes long, and in some cases, the positioning may be delayed. This poses a problem in that settling becomes unstable.

(Means for solving the problem) The present invention has been made in view of the above-mentioned circumstances,
The object of the present invention is to provide a magnetic disk device that can achieve stable settling.

In order to achieve this object, the present invention includes: a head actuator for moving a magnetic head in the radial direction of a disk; a timing generation circuit for detecting a sector servo signal recorded on the disk at a predetermined sampling frequency; a detection unit that detects the position of the magnetic head based on the detected sector servo signal and detects the moving speed of the magnetic head based on this position; and a detection unit that detects the position of the magnetic head based on the detected sector servo signal; a control unit that generates a braking signal based on the current position and movement speed, and switches between speed control and position control according to the distance to the target position track of the magnetic head;
The magnetic head includes a servo unit that generates a tracking servo signal during position control based on the detected sector servo signal, and an actuator drive circuit that drives the head actuator based on the tracking servo signal and the braking signal. Provided is a magnetic disk device characterized in that when the magnetic head reaches within a predetermined range of a target position track and switches from speed control to position control, a predetermined braking is applied to the moving speed of the magnetic head by the braking signal. It is something to do.

(Embodiment) Hereinafter, a preferred embodiment of the magnetic disk device according to the present invention will be described in detail with reference to FIGS. 1 to 5.

The magnetic disk device according to this embodiment stores a plurality of magnetic disk drives 2 as shown in FIG. 1, and a plurality of sectors SE are sequentially recorded on these magnetic disks 12 as shown in FIG. truck T. is formed.

Header signals SH extending in the radial direction of the magnetic disk 12 are radially recorded between each sector SH. Each sector SE is composed of a servo area, an index area, and a data area, and each area has a servo signal SA.

SS, S, index signal ID, data-CD Evening signal Data is recorded.

Further, the servo area extends over two tracks T and Tn+1 adjacent in the radial direction of the magnetic disk 12,
These servo areas are provided at four locations offset from each other in the circumferential direction, and as mentioned above, single-frequency servo signals S, 5S AB'C 80 are prerecorded in these servo areas by the magnetic head 1 for data recording and reproduction. be done.

And the arrangement of servo signals in this embodiment! It's a truck T. If T is an odd track, then this odd track T.

Servo signal SE is located at track center Tc, servo signal S6 is located on the outer circumference by 1/2 track width from track center TC, and servo signal S is placed on the inner circumference in fourth place! recorded as such.

Also, even track T. +1 center T, servo signal S
A is in place! Then, the servo signal S is sent to the outer circumferential side by 1/2 track width. , and the servo signals Sc are recorded so as to be located on the inner circumferential side.

Data signal D ate to the magnetic disk 12 as described above
The transmission and reception of the servo signals s, ss, s, etc. is performed via the magnetic helads 11 corresponding to each disk 12, and the transmission and reception from these magnetic helads 11 as shown in FIG.
The reproduced output as shown in FIG. 1 is supplied to a general data processing circuit 14 via a read/write amplifier 13.

The data processing circuit 14 extracts and processes the necessary data signal D atll and index signal ID from the reproduced output, and supplies the processed data etc. to the host device via an interface block (not shown).

On the other hand, the reproduction output from the disk 2 outputted from the read/write amplifier 13 is supplied to an integrating circuit 15 and a timing generating circuit 16, respectively.

-Here, this timing generation circuit 16 has the following functions as shown in FIG.
As shown in B), the delay F corresponding to the header signal SH
A C pulse (DPG) is supplied, and based on this delayed FG pulse, the ## signal portion between the header signal SH and the servo signal SA which is being reproduced and output is detected, and the signal as shown in FIG. 3(C) is detected. Generate a blank detection signal.

The timing generating circuit 16 generates a servo gate pulse Sa as shown in FIG. 3(D) using the falling timing of the blank detection signal as a reference.

The output timing of this servo gate pulse is synchronized with the timing of each output of the servo signals s and sss, and each servo signal s is output from the reproduction output.
, s , s , sD for A
BC, this servo gate pulse is generated for each sector, and the sector frequency is the sampling frequency ω,
(approximately 3.4 [kH2]).

This servo gate pulse is then supplied to the integration circuit 15, as well as the flash type A/D (analog-digital) converter 7, the detection circuit 18, and the servo circuit 1.
9.

Then, the integrating circuit 15 inputs each of the servo signals SA for a period corresponding to the pulse width of the servo gate pulse SG as described above, as shown in FIG. M3 (E).

Integrate S　S　S　S.

B'C' D Here, each of the above-mentioned servo signals S, 5S AB'C' SO is shifted from each other in the radial direction of the disk 12. The output level of each servo signal is determined according to the off-track amount of the magnetic helad 11. Excited.

Therefore, the peak levels of the integrated values of the respective servo signals integrated over the same integration period are different, and by comparing these peak levels, the amount of off-track of the magnetic gamma drive 11 can be determined.

Therefore, this integration circuit 15 samples the peak level of the integrated value of the servo signal as described above, and
The sampled peak level values La, L as shown in
b, Lc, and Ld are supplied to the A/D converter 17.

The A/D converter 17 digitizes the peak level value and outputs it to the detection circuit 18 and the servo 0 consultant 19.
supply to.

This servo circuit 19 receives each of the supplied servo signals sA,
Peak level values of sB, sc, and so.

Based on L, L, and Ld, a tracking servo signal S1 that corrects the off-track amount of the magnetic head 11 is generated, and this tracking servo signal S1 is
/A (digital-analog) is supplied to the converter 21.

The tracking servo signal S converted into analog by this D/A converter 21 is transmitted to the magnetic head 11 from the magnetic disk 12 via the actuator drive circuit 22.
The head actuator 23 drives the magnetic head 11 in the radial direction.
Off-track is corrected by driving according to the tracking servo signal Sr.

Note that when the magnetic helad 11 is tracing an even track, the servo circuit 19 calculates that W = L.
-L...(1)Cd Position error W, which is the off-track amount of the magnetic head, is expressed by the following formula:
Calculate n.

Similarly, when the magnetic head 11 is tracing an odd numbered track, the position error W is determined by the following formula: W = Ld - LC (2). Calculate.

Note that whether the track being traced by the magnetic head 11 is an odd numbered track or an even numbered track can be determined by comparing the levels of the peak level values L1 and Lb.

As a result of such calculation, the position error W. is magnetic herad 11
As shown in FIG. 4, the off-track amount varies approximately linearly around the track center TC of each track.

Then, the servo circuit 19 generates the above-mentioned tracking servo signal that reduces the position error to 0, and the generated tracking servo signal is commanded by the control circuit 20 (described later) during position control to be used as the D/ A converter 2
1 is output.

On the other hand, the peak level values, Lb, Lc, and Ld output by the A/D converter 17 are also supplied to the detection circuit 18,
This detection circuit 18 detects the position of the magnetic herad 11 based on the position error calculated based on these peak level values.

That is, each absolute position data of the current position track and the target position track is stored in this detection circuit 18 at the stage when the magnetic heald 11 starts moving, and the increase/decrease of the position error as the magnetic herad 11 moves. The absolute position of the magnetic head 1 is detected, and the distance to the target position track is calculated.

Further, this detection circuit 18 calculates the moving speed of the magnetic helad 1 based on the fluctuation in the sampling period (1/ω,) of the absolute position 1 detected as described above.

That is, if the absolute position fluctuation in one sampling period is Δt, the average moving speed of the magnetic head 1 in this sampling period is Δt・ωS+α(, α
is the amount of correction corresponding to acceleration or deceleration).

The detection circuit 18 then supplies the thus detected data on the distance to the target position track and the moving speed of the magnetic helad 11 to the control circuit 2o.

In this embodiment, when the distance to the target position track calculated as described above is a predetermined plurality of tracks (n), that is, when performing buffer theta, the control circuit 18 first performs speed control. Conduct, above D/A
A maximum velocity signal is provided to the actuator drive circuit 22 via the transducer 20.

As a result, during speed control in this magnetic disk device, the magnetic head 11 moves toward the target position track at high speed.

In this embodiment, the distance to the target position track of the magnetic head 11 is the predetermined plurality of tracks (n).
If the track is larger than 1/2, the control circuit 2
A speed control signal based on the speed control table memory in 0 is supplied to the actuator drive circuit 22 via the D/A converter 21.

The control circuit 20 also controls the distance ^i to the target position track calculated by the detection circuit 13 based on the peak level values supplied discretely every sampling period to within 1/2 track. When the speed control is stopped and the speed control signal is stopped, a braking signal is generated based on the accurate distance to the target position track and the moving speed at that time, and this braking signal is generated before switching to position control. The signal is supplied to the actuator drive diagram H122 via the D/A converter 21.

Note that the accurate distance to the target position track detected by the detection circuit 18 means that the peak level value is a discrete digital value for each sampling period (1/ωS). Exactly 1/2 from 1 track
It is not possible to detect that the target position has been reached within 1/2 track, and the distance to the target position track is calculated based on the first peak level value after reaching within 1/2 track.

The braking signal is set to be larger as the exact distance to the target position track is smaller when the magnetic head 11 reaches within 1/2 track from the target position track, and is set to be larger as the moving speed at that time is larger. magnetic herad 1
The moving speed of No. 1 is experimentally set so as to be within a range where position control is possible near the track center of the target position track, that is, a speed that is neither too large nor too small.

As a result, according to this magnetic disk device, when the magnetic helad 11 reaches within 1/2 track of the target position track and switches from speed control to position control, the accurate distance to the target position track at this time and this information can be determined. The movement of the magnetic heald 11 can be braked depending on the moving speed of the magnetic heald 11 at the time.

Therefore, the moving speed when not switching to position control is too high and the magnetic helide 11 does not overrun the target position track.

In addition, by applying braking to prevent the moving speed from becoming too low at this time, settling time in position control as described above does not take long.

The control circuit 20 causes the servo signal 19 to output the tracking servo signal S1 to perform position control at the same time as the braking is finished as described above.

Next, the operation of the magnetic disk device configured as described above will be explained in the fifth section.
This will be explained using the flowchart shown in the figure.

First, this magnetic disk device generates servo signals SA, Sa, and Sc by the magnetic head 11.

To reproduce the SD, step 1), based on these servo signals, the servo circuit 19 generates a tracking servo signal based on the position error, and the detection circuit 18 also detects the position of the magnetic herad 11 based on the position error, etc. and detect the moving speed (step 2).

Thereafter, the distance to the target position track is calculated based on the detected position of the magnetic head 11, and the control circuit 20 calculates the distance to the target position track.
It is determined whether the distance is greater than or equal to a predetermined plurality of tracks (n) (step 3).

If the distance is above, the control circuit 20 outputs a maximum speed signal to set the moving speed of the magnetic nod 11 to the maximum distance (step 4), and if the distance is 1/ It is further determined whether there are more than or less than two tracks (Step 5).

In the above case, a speed control signal based on the speed control table memory is output (step 6), and a predetermined speed is set to perform speed control (step 7).

On the other hand, if the distance to the target position track is less than 1/2 track, the control circuit 20 generates a braking signal at a predetermined level as described above, stops speed control (step 8), and Magnetic nod 11 with braking signal
A brake is applied to the movement of (step 9).

Thereafter, the control circuit 20 causes the servo circuit 19 to output a tracking servo signal ST to perform position control (step 10), and positions the magnetic nod 11 on the target position track.

As described above, according to the magnetic disk device according to the present embodiment, the movement of the magnetic nod 11 is braked between speed control and position control during buffer seek, and this braking is changed from speed control to position control. Magnetic nod 1 when switching
The moving speed of the magnetic head 11 near the track center of the target position track can be controlled within a desired speed range by appropriately varying the distance to the target position track 1 and the moving speed. .

Therefore, it is possible to eliminate problems such as overrunning the target position track due to the speed being too high when switching by position control, or requiring a long time for settling due to the speed being too low at this time. Settling can be achieved.

Moreover, according to the present embodiment, the method is similar to the conventional example? Since an external school such as a vI R element or a magnetized disk is not required, thermal off-track does not occur.

In this embodiment, the detection circuit 18 and the servo circuit 19 are
Although the control circuit 20 and the control circuit 20 are each constructed from independent circuits, the present invention may use a microcomputer having each of the functions of these circuits 18, 19, and 20.

In that case, detection of the positional error, or detection of the position and moving speed of the magnetic head 11 may be performed by calculations based on a predetermined program.

(Effects of the Invention) As is clear from the above description, the present invention provides a head actuator for moving a magnetic head in the radial direction of a disk, and a timing for detecting a sector servo signal recorded on the disk at a predetermined sampling frequency. a generating circuit; a detecting section that detects the position of the magnetic head based on the detected sector servo signal and detects the moving speed of the magnetic head based on this position; a control section that generates a braking signal based on the position and moving speed when the magnetic head reaches the target position, and switches between i-degree control and position control according to the distance to the target position track of the magnetic head; and the detected sector servo. a servo unit that generates a tracking servo signal during position control based on the signal; and a servo unit that generates a tracking servo signal during position control based on the signal, and a
and an actuator drive circuit that drives the throat actuator, and when the magnetic head reaches within a predetermined range of the target position trunk and switches from speed control to position control, the braking signal changes the magnetic head to the throat movement speed. Since a predetermined amount of braking is applied, stable settling can be achieved, and as a result, reliable and quick access control of the magnetic head can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the magnetic disk device according to the present invention, FIG. 2 is a diagram showing the signal format of the magnetic disk, and FIG. 3 is a diagram showing waveforms of various parts in the embodiment shown in FIG. 1. FIG. 4 is a diagram showing the positional relationship between positional errors and signal formats; FIG. 5 is a flowchart showing operating conditions; FIG. 6 is a plan view showing the main parts of a conventional magnetic disk drive; FIG. is a waveform diagram showing the detection output of the I'vl element. 11...Magnetic head, 12...Disk, 16...
・Timing generation circuit, 18...detection circuit (detection section)
, 19... Servo circuit (servo section), 20... Control circuit (control section), 22... Actuator drive circuit,
23...Head actuator. Kuku 4 figure 7m

Claims (1)

[Scope of Claims] A head actuator that moves a magnetic head in the radial direction of a disk; a timing generation circuit that detects a sector servo signal recorded on the disk at a predetermined sampling frequency; and a timing generation circuit that detects a sector servo signal recorded on the disk based on the detected sector servo signal. a detection unit that detects the position of the magnetic head based on the position and detects the moving speed of the magnetic head based on this position; a control unit that generates a braking signal based on the magnetic head and switches between speed control and position control according to the distance to the target position track of the magnetic head; and a tracking servo control unit that performs position control based on the detected sector servo signal. a servo unit that generates a signal; and an actuator drive circuit that drives the head actuator based on the tracking servo signal and the braking signal, and when the magnetic head reaches within a predetermined range of the target position track, the position is changed from speed control to position. A magnetic disk device characterized in that when switching to control, a predetermined braking is applied to the moving speed of the magnetic head by the braking signal.