JPS6326814A - Head positioning control circuit for magnetic head device - Google Patents

Abstract

PURPOSE:To prevent malfunction due to defect of a medium by detecting a deviation of a data head from an object track, and returning the head positioning for data face servo information to the head positioning for servo face servo information. CONSTITUTION:A control circuit 20 detects a data face servo information recoding area by using a signal obtained by counting a distance from an index mark read from a magnetic disk 10 and controls a position signal separation circuit 1 to extract the data face servo information read by a data head 9. The servo information is fed to a position error detection circuit 2 to detect a deviation of the head 9 from an object track and fed to an error ampilfier circuit 14 to correct a position error by the servo face servo information read by a servo head 8l. A medium deffect detection circuit 3 detects a defect of medium from an output of the circuit 2 to block the output transmission of output of the circuit 2 by the off-state of a switch 4.

Description

[Detailed Description of the Invention] [Summary] When the head is positioned using the servo information recorded on the servo surface, and when the head is positioned again using the servo information recorded on a predetermined area of the data surface, the data surface is If there is a media defect in a defined area, the media defect should be removed to prevent the head from being incorrectly positioned and causing malfunctions such as writing into adjacent tracks or causing read errors. Upon detection, the head positioning control based on the data surface servo information is stopped, and the positioning operation is returned to using the servo surface servo information.

[Industrial application field]

The present invention relates to a magnetic disk device that positions a head on a servo surface and then repositions the head on a predetermined area of a data surface, and in particular malfunctions when a medium defect exists in a predetermined area of the data surface. The present invention relates to a head positioning control circuit for a magnetic disk device that prevents this.

A magnetic disk used in a magnetic disk device is usually composed of multiple recording media, and one of the multiple recording surfaces is used as a servo surface to record servo information for positioning the head to the target cylinder. There is.

By the way, magnetic disk devices are required to improve their recording density, and the spacing between tracks on the data surface is becoming shorter.
Due to differences in the expansion and contraction of the recording medium and the arm that attaches the head due to temperature changes, etc., even if the head is positioned at the target cylinder using the servo information on the servo surface, each track provided on multiple data surfaces on the same cylinder may Therefore, it has become difficult to always accurately position the head.

For this reason, after the head is positioned using servo information on the servo surface, the head is precisely positioned on the target track again based on the servo information number recorded in a predetermined area on the data surface.

In this case, a media defect in a defined area of the data surface may cause data to be written to adjacent tracks or
It is necessary to prevent malfunctions such as errors in read data.

[Conventional technology]

FIG. 3 is a diagram illustrating an example of data surface servo.

One circumference of the magnetic disk 10 is divided into n equal parts, and data surface servo information is recorded at each boundary indicated by ■ to ■.

In other words, if the lines indicated by [phase] to @ are each track, the boundaries of track ■ such as ■ to ■ have servo information N between them and the adjacent track 0, and servo information S between them and the track @. is recorded, and then servo information S is recorded between the track [phase]
However, servo information N is recorded between track @, further servo information N is recorded between trunk [phase], servo information S is recorded between track 0, and furthermore, servo information N is recorded between track [phase]
Servo information S is recorded between the track [phase] and servo information N is recorded between the track [phase], and thereafter, a predetermined number of servo information are recorded in the same manner repeatedly.

For example, when the head is positioned on track 0, the following servo signal is obtained depending on the relative position of the head and track (2). In other words, the head ■ is located between the track ■ and the track 0, and the servo information read by the head ■ has the waveform shown by the arrow. The height of the waveform is large,
Servo information NN and S have opposite polarities.

Also, the servo information read by head ■ is the waveform shown by the arrow, ■
Since the waveform of the opposite polarity on the track @ side is read by the amount closer to track 0 than that, the waveform is canceled by that amount and the height of the waveform becomes lower. Since the servo information read by the head (2) is accurately positioned on the track (2), the servo information InN and S on the track [phase] side and the trunk 0 side cancel each other out and form a straight line.

The servo information read by the head (2) is the waveform shown by the arrow, and since it has passed track 0 and shifted in the direction of the track @, a waveform with the opposite polarity to that of the head (2) is obtained.

Since the head ■ has further shifted significantly towards track 0,
A large waveform can be obtained as with head ■.

Therefore, is the head positioning system based on data surface servo? 11
One circuit controls the waveform of the servo information read by the data head to become small, and ultimately maintains the state in which the waveform based on the servo information does not appear.

By the way, in the head positioning control circuit of a conventional magnetic disk device, when the servo information provided on the data surface cannot be read due to a defect in the medium, the waveform indicated by ◎ or [phase] becomes smaller as indicated by the dotted line, and this waveform If it cannot be read, there is a drawback that it may be positioned at the wrong position. Therefore, in order to remedy this problem, a magnetic disk with no medium defects has been selected and used for the area on the data surface where servo information is recorded.

[Problem that the invention seeks to solve]

As mentioned above, conventionally, a magnetic disk with no media defects is selected for the area where servo information is recorded on the data surface, but it is difficult to produce a magnetic disk medium without defects, and the assembled magnetic If, as a result of checking the disk, there is a defect in even one of the servo information recording areas on the plurality of data recording surfaces, the magnetic disk medium must be replaced, which poses a problem in that the magnetic disk device becomes extremely expensive.

In view of these problems, the present invention provides a circuit for detecting media defects. When a defect is detected in the data surface servo information recording area, head positioning based on the data surface servo information is stopped, and positioning operation using the servo surface is resumed. The aim is to bring it back to .

[Means for solving problems]

FIG. 1 is a block diagram of the principle of the present invention.

The servo radar 8 reads servo information from the servo surface of the magnetic disk 10 and sends it to the position detection circuit 11. The position detection circuit 11 sends position information of the servo head 8 to a pulse generation circuit 19, an error amplification circuit 14, and a speed detection circuit 13.

The pulse generation circuit 19 sends out a pulse each time the servo head 8 crosses a track, and sends it out to the subtraction counter 18 .

The control circuit 20 sets the distance to the target track in the subtraction counter 18, and the subtraction counter 18 subtracts this cented distance by the pulse sent out by the pulse generation circuit 19.
It is sent to the target speed creation circuit 17.

The target speed generation circuit 17 sends the target moving speed of the servo head 8 to the speed error amplification circuit 16 according to the moving distance of the servo head 8.

The speed detection circuit 13 detects the actual moving speed of the servo head 8 from the current detected by the current detection circuit 12 that drives the linear mokuroscope by the power amplifier circuit 5 and the position of the servo head 8 detected by the position detection circuit 11. The signal is sent to the speed error amplification circuit 16.

The speed error amplification circuit 16 drives the power amplification circuit 5 via the switch 15 based on the difference between the target speed and the actual speed, and the linear motor 6 moves the carriage 7 based on the drive of the power amplification circuit 5 to drive the servo head 8. and move the data head 9.

When the servo head 8 reaches the vicinity of the target track, the control circuit 20 switches the switch 15 and sends the output of the error amplifier circuit 14 to the power amplifier circuit 5.

The error amplification circuit 14 includes the speed detection circuit 13 and the position detection circuit 1.
A position control signal is generated from the output of the position error detection circuit 1 and the position error detection circuit 2, and control is performed so that the data head 9 is accurately positioned on the target track.

The control circuit 20 uses a signal obtained by a counter operated by a clock generated from servo information (not shown) to count the distance from the index mark read from the magnetic disk 10, as shown in FIGS. The data surface servo information recording area is detected, and the position signal separation circuit 1 is controlled to extract the data surface servo information read by the data head 9.

The data surface servo information extracted by the position signal separation circuit 1 enters the position error detection circuit 2, and is then input to the data head 9 as described above.
The deviation from the target trunk is detected and sent via the switch 4 to the error amplification circuit 14 to correct the device error constituted by the servo surface servo information read by the rad 8 to the servo.

When the medium defect detection circuit 3 detects a medium defect from the output of the position error detection circuit 2, it controls the switch 4 to disconnect the circuit as shown by the dotted line and prevents the output of the position error detection circuit 2 from being sent.

[Effect]

With the above configuration, the position error detection circuit 2 can detect the positional deviation of the data head from the target trunk based on the data surface servo information, and can correct the position error using the servo surface servo information. 3 detects a media defect in the area where data surface servo information is recorded.
Stops position error correction based on data surface servo information,
The head positioning operation can be performed using only the servo surface servo information.

〔Example〕

FIG. 2 is a schematic diagram of a circuit showing an embodiment of the present invention.

FIG. 2 is a detailed block diagram of the position error detection circuit 2 and medium defect detection circuit 3 shown in FIG. The servo information that enters from the position signal separation circuit 1 via (2) has a waveform as shown in FIG.
It is held at 2.

The peak hold circuit 21 receives a sample pulse input from terminal A, for example, as shown by the solid line of sample pulse A in FIG.
Extract the peak value of servo information and use peak hold circuit 2
2 extracts the peak value of the servo information using the sample pulse indicated by the solid line of the 311il sample pulse B input from the terminal B;

Therefore, in the case of the head ■, for example, the peak hold circuit 21 extracts the waveform shown by [phase] and ■ in FIG. 3 and holds its peak value, and does not extract the waveform shown by ■ and @l. Also, the peak hold circuit 22 has a 0. Extract the waveform shown by ■,
[Phase], waveforms indicated by 0 are not extracted. That is, every other one is extracted.

These sample pulses A and B are generated by a known technique from the position detection circuit 11 in FIG. 1, and are switched between being shown as a solid line and as a dotted line depending on whether the cylinder is odd or even numbered.

That is, the servo information between track [phase] and 0 shown in FIG. 3 and the servo information between tracks This is because the polarity is reversed, so it is necessary to always extract only waveforms of the same polarity.

Therefore, in the case of head ■, the peak hold circuit 21 is [
phase], the waveforms indicated by ■ are extracted and their peak values are held, and the waveforms indicated by ■ and ◎ are not extracted. Further, the peak hold circuit 22 extracts the waveform indicated by 0.0, and does not extract the waveform indicated by [phase] or ■.

The output of the peak hold circuit 21 is sent out with the same polarity by the operational amplifier circuit 23, and
The output of No. 2 is sent out with its polarity inverted by the operational amplifier circuit 24. The outputs of the operational amplifier circuits 23 and 24 are added together in the adder circuit 26, resulting in a current whose magnitude corresponds to the amount of deviation from the target track.
is sent as a position error signal.

Further, the outputs of the operational amplifier circuits 23 and 24 are sent to the operational amplifier circuit 25.
The difference between the outputs is detected, and the operational amplifier circuits 27 and 28
is supplied to If there is no defect in the medium, the operational amplifier circuit 25
The output of is O, and if there is a defect, a positive or negative voltage is delivered.

The operational amplifier circuit 27 compares this voltage with a threshold value of 10 and the operational amplifier circuit 28 compares it with a threshold value of -. It is sent as a signal.

〔Effect of the invention〕

As explained above, in the present invention, when there is a defect in the data surface servo information recording area, the positioning operation returns to the servo surface servo information, so there is no malfunction and there is no need to select an expensive magnetic disk medium. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention, and FIG. 3 is a diagram illustrating an example of data surface servo. In the figure, 1 is a position signal separation circuit, 2 is a position error detection circuit, 3 is a medium defect detection circuit, 4.15 is a switch, 5 is a power amplifier circuit, 6 is a linear morph, 7 is a carriage,
8 is a servo head, 9 is a data head, 10 is a magnetic disk, 11 is a position detection circuit, 12 is a current detection circuit, 13 is a speed detection circuit, 14 is an error amplification circuit, 1
6 is a speed error amplification circuit, 17 is a target speed creation circuit, 18
is a subtraction counter, 19 is a pulse generation circuit, 20 is a control circuit, 21.22 is a peak hold circuit, 23, 24, 25.27, 28 is an operational amplifier circuit,
1st use

Claims (1)

[Claims] Head positioning is performed using servo surface servo information recorded on the servo surface, and precise head positioning control is performed again based on the data surface servo information recorded in a predetermined area of the data surface. In a magnetic disk device that performs means for comparing the signal with a threshold value and, if the threshold value is exceeded, preventing the transmission of the head position control signal transmitted by the position error detection circuit (2);
3) A head positioning control circuit for a magnetic disk device characterized by providing (4).