JPH02297703A - Head switching system in sector servo - Google Patents

Abstract

PURPOSE:To quickly perform the switching of a head even when an offset exists between a current head and a targeted head by providing an offset detecting means and an offset applying means. CONSTITUTION:The offset detecting means 3 and the offset applying means 4 are provided. When switching from the current head 1A to the targeted head 1B is performed, an offset value between the current head 1A and the targeted head 1B is applied from the offset applying means 4 to a position servo circuit 2 as leaving the current head 1A as it is, and after on-track being performed, the head is switched to the targeted head 1B. After the head is switched, the targeted head 1B is nearly set at an on-track state, therefore, only a small magnitude of current to be applied on a VCM 7 is required, then, a static condi tion can be immediately obtained. In such a way, it is possible to accelerate convergence to the on-track.

Description

[Detailed Description of the Invention] [Summary] Regarding the switching of the recording/reproducing head in a sector servo type disk storage device, such as a magnetic disk device, the purpose of this invention is to improve convergence to on-track immediately after switching the head, and to perform multiple recordings. /In a disk-type storage device equipped with a reciprocating head and using sector servo, the offset value in the cross-track direction between each recording/reproducing head is detected and stored, and the offset value between the currently selected head and the next head is detected and stored in response to a request. head switching means; an offset detecting means for outputting an offset value between the target head to be selected; and an offset applying means for converting the offset value outputted by the offset detecting means into an analog quantity and applying it to a position servo circuit; When
The current head is configured to apply an offset value between the current head and the next selected target head to the position servo circuit to bring it on-track, and then switch to the target head (1B).

[Industrial application field]

The present invention relates to recording/reproducing head switching in a disk type storage device, such as a magnetic disk device, and particularly to improving on-track convergence immediately after head switching in a sector servo type disk type storage device.

[Conventional technology]

In a storage device having multiple disk media, such as a magnetic disk device, switching to another magnetic head on the same cylinder (a cylinder circumscribing the same numbered track of each disk) (this is called a head change) is often done.

FIG. 6 is a diagram showing an example of the configuration of a magnetic disk device.

A magnetic disk 102 is mounted on the hub of a DC motor 104 attached to a pace 107 via a spacer 105.
Disc clamp 10 is made of one disc or multiple discs stacked together.
It is fixed by 6. A magnetic head 101 is provided so as to face each surface of the magnetic disk 102. The magnetic head 101 is supported by a head arm (not shown) via a spring arm 103, and is supported by an actuator (not shown) (voice coil motor). ), the magnetic disk 102 is movable in a direction perpendicular to the direction of rotation of the disk.

Servo systems for positioning the magnetic head on a track include a servo surface servo system and a sector servo system. In the servo surface servo method, a servo signal is written on the inner surface of a magnetic disk medium as a servo surface, and the cylinder is positioned by the servo signal read by a servo head provided on the servo surface. On the other hand, the sector servo method does not provide a specific servo surface, but instead writes servo information as shown in Figure 7(a) in each sector of all disk surfaces. Consists of number code (gray code) and servo signal. The servo signal is read by a head that performs normal read/write operations, and the head is positioned by controlling the read amplitudes of the servo signals A and B to be equal, as shown in Figure (b). . In the sector servo method, all disk media surfaces can be used for data, so the usage efficiency of the media surface is high.

In the servo surface servo method, head positioning control is always performed by a read signal from the servo head, and switching between read/write heads has no effect on head positioning control.

In the sector servo system, when switching heads, the track tracking operation becomes momentarily uncontrolled.

When the head that is currently tracking a track (current head) is switched to another head (target head), there will be no problem if the target head is completely on track, but if the head is off track by several microns. In modern magnetic disk drives that suffer from this problem, it is rare for the target head to be on trunk after head switching, and in most cases there is a deviation of several microns between each head.

FIG. 8 is a diagram showing operations during a conventional head change.

In the state shown in FIG. 8(a), the bead 18 is on the track 10.
8, head 1B is offset from above trunk 108 by typically several microns.

When the head is changed to head 1B in the above condition, the state shown in FIG. 1B is reached, but during the head change there is a momentary uncontrolled state, and the subsequent movement of head 1B is due to the offset. Then, a trajectory as shown in FIG. 3(C) is followed.

In FIG. 8, for the sake of explanation, the current head 14 and the target head 2B are
Although the heads are opposed to both sides of the same disk, the target head may be any head within the device. In the figure, the hatched head indicates a head that is enabled for reading/writing (selected).

[Problem to be solved by the invention]

As explained above, when switching heads, an off-trunk occurs the moment the target head is moved, so a relatively large current flows to the voice coil motor (VCM) to keep it on track, as shown in Figure 8. As shown in C), the convergence to on-track was poor, and it took a long time to settle to on-track.

The problem to be solved by the present invention is to provide a head switching method that solves the above-mentioned conventional problems.

[Means to solve the problem]

FIG. 1 is a block diagram showing the configuration of the present invention.

In the figure, l is the read/write head.

The mouth is the current head that is currently selected, and 1B is the target head that will be selected next.

A position servo circuit 2 calculates a position error from the sector servo signal currently read out by the head 1A, creates and outputs a position control signal.

3 is an offset detection means, and each recording/reproducing head 1
The offset value between the currently selected head 1A and the next selected target head 1B is output in response to a request.

4 is an offset applying means, and an offset detecting means 3
The output offset value is converted into an analog quantity and applied to the position servo circuit 2.

5 is a seek control circuit, which currently tracks (cylinder)
Creates and outputs a control signal for movement from to the target track (cylinder).

A power amplifier 6 power-amplifies the output of the position servo circuit 2 (when on-track) or the seek control circuit 5.

A voice coil motor (VCM) 7 is driven by the output of the power amplifier 6 to position the recording/reproducing head group 1.

8 is a head selection circuit, which selects a plurality of recording/reproducing heads 1;
Select and connect the commanded one.

[For production]

In the present invention, an offset detecting means 3 and an offset applying means 4 are provided, and the current head 1A is changed to the target head 1B.
When switching to the current head LA, the offset applying means 4 applies an offset value between the current head l^ and the target huff 118 to the position servo circuit 2, and after on-tracking, the target head 1B is switched. Let's switch.

The human power of the power amplifier 6 that drives the VCM 7 is applied to the output of the seek control circuit 5 during seek, but is switched to the position servo circuit 2 during on-track.

The offset detection means 3 measures the offset between each head when the power is turned on and at regular intervals, stores this, and when switching heads, when the current head number and the target head number are input, the offset between the heads is detected. Read and output the offset between.

The offset applying means 4 converts the input offset value into D.
/A conversion (digital/analog conversion) and applied to the position servo circuit 2.

Before the offset value is added, the position servo circuit 2 controls the current head 1A to be on-track, as shown in FIG. Off-track by a corresponding amount of deviation. In this state, when an offset value X is added, the position servo circuit 2 controls the current head 1A to be offset by X, as shown in FIG. It becomes what it is.

When on-track is achieved with an offset applied, head switching is performed and offset application is stopped. The state at that time is as shown in FIG. 2(C). In FIG. 2, the head with hatching is selected,
A read/write head is shown.

In this way, after head switching, the target head 1B is almost on track, so the current applied to the VCM 7 at the time of switching is very small and immediately becomes static. The trajectory of the head becomes as shown in FIG. 2(d), and the convergence to the on-trunk becomes very fast. In FIG. 2(d), the difference between position Q and position P corresponds to offset X.

[Example〕 FIG. 3 is a diagram showing the configuration of an embodiment of the present invention.

In the figure, l is a head, 6 is a power amplifier, 7 is a VCM 7, 8 is a head selection circuit,
This is the same as shown in FIG.

2 is an on-track controller, which is a position servo circuit that calculates a position error from a sector servo signal read by the head and creates a position control signal by combining a component proportional to the position error, an integral component, and a differential component.

Reference numeral 3 denotes an offset detector which measures and stores the offset between each head when the power is turned on and at regular time intervals, and outputs the offset between both heads upon input of the current head number and target head number when switching heads.

The offset between each head is 5 qt for one spatula Fa, and when head a is on track, other heads such as b
The offset is calculated from the read data of the sector servo signal without performing on-track control. As shown in FIG. 4, the measurement results are for 54 heads a and for the other heads b and c.

-, offset value of n Omb+ Oac+ "-'
+Oan is stored in the memory as a table in which it is written. When switching heads, the current head number (for example, C
) and the target head number (for example, f) are input, the offset value OCf of the heshitogo for head C is inputted.
Calculate from t-Oa f Om c and output.

4 is an offset applicator, which converts the offset value output from the offset detector 3 into a D/A and applies it to the on-track controller 2.

5L 52.53.54.55 constitutes a seek controller, which positions the head to a target track (cylinder) in response to a seek command.

The remaining seek amount calculator 51 always holds the current track number from the input track crossing pulse, and calculates the remaining seek amount from the input track crossing pulse to the track number indicated by the seek command.

The target speed generator 52 reads and outputs the target speed corresponding to the calculated remaining seek amount.

The speed generator 53 reads the track number (gray code) in the sector mark signal read by the head at regular sampling times and calculates the current speed of the head.

The speed error generator 54 calculates and outputs a speed error from the input target speed and current speed.

The FF generator 55 generates a control signal for decelerating in a predetermined pattern during deceleration.

A head switching controller 9 controls switching from the current head to the target head specified by the command in response to a head switching command.

Reference numeral 21 denotes an on-track completion detector, which detects on-track completion when the error signal stabilizes to 0 in the on-track controller 2 after applying the offset, and transmits the on-track completion signal to the head selection circuit 8 and the offset applicator 4.
Send to.

FIG. 5 is a flowchart showing the operation of one embodiment of the present invention.

The operation will be described below according to the processing steps in the flowchart.

■When the head switching controller 9 receives a head switching command in the on-trunk control state, the head switching controller 9 responds to the command by:
First, the current head and target head numbers are indicated to the offset detector 3, and then the target head number is indicated to the head selection circuit 8, and a head switching preparation command is issued. The offset detector 3 calculates and outputs an offset value between the two heads from the input numbers of the current head and the target head.

(2) The offset applicator 4 compares the input offset value with a predetermined darkness value, and if it is less than the darkness value, it sets the offset value ζO and jumps to step (2), and if it is greater than the darkness value, it proceeds to step (2).

(2) The offset applicator 4 performs D/A conversion on the offset value and applies it to the on-track controller 2.

(2) The on-track controller 2 performs on-track control based on the servo signal and the applied offset. The on-track completion detector 21 detects the completion of on-track when the error signal is fixed at O in the on-track controller 2, and sends an on-track completion signal to the head selection circuit 8 and the offset applicator 4. do.

(2) When the offset applicator 4 receives the on-track completion signal, it stops applying the offset.

(2) The head selection circuit 8 receives the on-track completion signal and executes switching to the target head specified by the head switching preparation command. In the on-track controller 2,
On-track control is performed using the servo signal read from the switched head, and the head switching operation is completed.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, even if there is currently an offset between the head and the target head, smooth and quick head L/LJ switching operation is possible, improving the data processing capacity of magnetic disk drives, etc. This has a significant industrial effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a diagram showing the head switching operation according to the present invention, FIG. 3 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 4 is a diagram showing the offset value. FIG. 5 is a flowchart showing the operation of an embodiment of the present invention; FIG. 6 is a diagram showing an example of the main part configuration of a magnetic disk device; FIG. 7 is a sector servo signal. 8A and 8B are diagrams showing operations during head switching according to a conventional example. In the figure, 1, 1A, 18, 101 are recording/reproducing heads, 2
is a position servo circuit (on-track controller), 3 is an offset detection means (device), 4 is an offset application means (device), 5 is a seek control circuit, 6 is a power amplifier, and 7 is a VCM
, 8 is a head selection circuit, 9 is a head switching controller, 21 is an on-trunk completion detector, 5I is a remaining seek amount calculator, Af target speed generator, 53
is a speed generator, 54 is a speed error generator, 55
is an FF generator, 102 is a magnetic disk, 10
3 is a spring arm, 104 is a motor, IO5 is a spacer, 106 is a disk clamp, 107 is a base, and 108 is a track. : Ko; 111.6 twilight, 11.11. 1. Block diagram showing the configuration of the present invention.
) (C) (d) Figure 2 showing the head switching operation according to the present invention.
Figure 1 shows an example of storing offset values and an example of offset calculation.
Figure 4 is a flowchart showing the operation of an embodiment of the present invention.
5 Figure 6 shows an example of the main part configuration of a magnetic disk device.
Figure 7 shows the sector servo signal.

Claims (1)

[Claims] In a disk type storage device including a plurality of recording/reproducing heads (1) and using sector servo, an offset value in the cross-track direction between each recording/reproducing head (1) is detected and stored. an offset detection means (2) for outputting an offset value between the currently selected current head (1A) and the next selected target head (1B) in response to an offset request; An offset applying means (4) converts the output offset value into an analog value and applies it to the position servo circuit (2). A head switching system in sector servo, characterized in that the head switching method in sector servo is characterized in that the offset value between the target head (1B) to be selected is applied to a position servo circuit (2) and the head is on-track, and then the target head (1B) is switched to the target head (1B).