JPS6070562A - Positioning method of magnetic head - Google Patents

Abstract

PURPOSE:To attain surely positioning to a required track by positioning a magnetic head on the basis of a positional error when the magnetic head exists within a prescribed positional error; and only when the magnetic head exceeds the prescribed positional error, positioning the magnetic head on the basis of a track number and the positioning error. CONSTITUTION:The magnetic head positioning control circuit is provided with an adder 9 for composing a detected track number TRa with accurate positional information FPa, a subtractor 10 finding out the difference between a track No. TRd from a track number setting circuit 6 and the output of the adder 9, a comparator 13 comparing a limit value K from a reference positional error setting circuit 12 with an output FPa from an accurate positional information detecting circuit 8, and when FPa>K, outputting a logical ''1'' signal SWc, and a switch 14 selectively switching an output applied from the subtractor 10 or the output of the circuit 8 by the signal SWc. Only when the shear of the track exceeds a prescribed limit value, the track number also is referred to control the position, so that data reading or writing from/to an incorrect track is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for positioning a magnetic head, and more specifically to a method for positioning a magnetic head, and more particularly to a method for positioning a magnetic head in a rack type magnetic disk drive. The present invention relates to a method for positioning a magnetic head using a control circuit.

Background of the technology, conventional technology, and problems In order to improve the positioning accuracy of the magnetic head of a magnetic disk drive, the position signal written in advance on the magnetic disk surface is returned to the magnetic disk, and the track position changes due to the deviation of the center of rotation of the disk or thermal expansion. Servo track systems that are not affected are already known.

In addition, in devices with a small number of magnetic disks, an embedded servo system is known in which information and data coexist on the same medium surface in order to increase the ratio of data storage capacity to the total storage capacity of the medium (servo information child data). However, in this method, a method is often adopted in which a delay coded track number and precise position information are stored in advance as servo information. In such a system, a magnetic head is moved from a certain track to a desired track.
Conventionally, there are the following methods for locating the desired track (so-called "tracking") in order to read or write data (so-called "seek").

The first method uses only precise position information among the read servo information as a position error and controls the positioning of the magnetic head so that this becomes zero. Since this method does not use track numbers, if a large positional shift occurs due to some kind of failure, the position will be placed on a different track than the desired track, and this error will not be detected and an abnormal access will occur. There is a possibility that it will be carried out.

Another method is to always use the track number and precise location information and control these to equal the desired trunk number. However, with this method, if a media defect or dust adheres to the address code previously written on the recording medium on the magnetic disk surface and the track number is read incorrectly, there is a possibility that the device may be positioned on the wrong track. It is full of fruit. In order to prevent this, it is possible to add redundancy by returning the same code twice when writing a code, and checking it on the reading circuit side. There is a problem that the capacity ratio decreases and the 1ljlJ f11 circuit becomes complicated because the reading circuit performs the determination process.

OBJECTS OF THE INVENTION An object of the present invention is to provide a magnetic head positioning method that solves the problems in the prior art described above and can reliably position a magnetic head on a desired track using a relatively simple circuit.

Structure of the Invention The above-mentioned object of the present invention is to take into account that precise position information is more reliable than track numbers, and if the position error obtained from the precise position information is within a specified value, use that position error to calculate the specified value. This is achieved based on the idea of controlling using the track number only when the value exceeds the value.

That is, in the present invention, a magnetic head reads servo information having a track number and position information stored in advance along each track on the surface of a magnetic disk medium.
In the magnetic head positioning method in which the magnetic head is positioned on a predetermined track by negative feedback of the read servo information, during the tracking period after the magnetic head is once positioned on the predetermined track, the read If the precise position information of the servo information obtained from the above is within a predetermined position error, the magnetic head is positioned based on the position error, and if the precision position information of the read servo information is within a predetermined position error, the track number and the read servo information are determined. A method for positioning a magnetic head is provided, characterized in that the magnetic head is positioned based on a positional error.

Embodiment of the Invention An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a magnetic head positioning control circuit and related parts of a magnetic disk device. In FIG. 1, a magnetic disk 1 is rotated by a spindle motor 2, and a magnetic head 3 floats while maintaining a predetermined gap from the rotating surface, and is slid and positioned on a predetermined track by a drive mechanism 4.

The control circuit includes a servo information reading circuit 5 that reads servo information detected by the magnetic head 3, a track number detection circuit 7 that receives servo information from the reading circuit and extracts a track number, and extracts precise position information from the servo information. It has a precise position information detection circuit 8. In addition, the control circuit is
An adder 9 that combines the detected track number TR & with the detected precise position information FPa, a track number setting circuit 6 that sets a desired track number, and the desired track number TR from the setting circuit 6 and the above addition. Output of device 9 (TRa
It is equipped with a subtracter 10 that calculates the difference of 10 FPa). Furthermore, the control circuit includes a reference position error setting circuit 12 that sets a limit value of position error, and compares the limit value of the setting circuit 12 with the output FPa'i of the precise position information detection circuit 8, and
A comparator 13 which outputs a signal SWc of logic "1" when L,>K, and a switch 14 whose contacts are switched by the signal SWc to selectively switch the applied output of the subtracter 10 or the output of the circuit 8. , and an amplifier 11 that amplifies the output of the switch 14 and outputs it to the drive mechanism 4.

As before, the surface recording medium j~ of the magnetic disk 1 has a plurality of tracks n''-1r n rn as shown in FIG.
+1 are provided concentrically, and for each track, for example, for n tracks, 1st servo information S, data recording section D1, . . . , 100th servo information 5100,
Data recording sections D100 are arranged continuously. The first servo information S1 and data storage section D1 are detailed in FIG. The servo information S1 is composed of a servo mark section SM, a code section C0DX'8, and a dense position information section PPI.

In the code section COD, a track address is digitally recorded, and in the precise position information section PPI, information that allows detection of positional deviation within one track is recorded.

In the precise position information section, a pattern is written in advance that is shifted by 1/2 tora from the center of the track and has a phase difference between every other track.

In Fig. 4, the head position "f", which is correctly positioned at the center of the nth track, is P2, and the head position when a track deviation of 1/2 track to one side occurs is P1, the head position is 1/2 track shift to the other side. If the head position in this case is B3, the read waveforms of the Pl head are only AI and A2, and conversely, the read waveforms of B3 are only B1 and B2.

If B2 is located correctly, AI, Bl, A2.
B2 is detected with the same amplitude. In this way A1 and B
The amount of deviation from the correct position can be determined by taking the photographing width difference of 1, the withdrawal width difference of A2 and B2, or the average of both. 1 more
From the sign of the amplitude difference and the least significant bit (even/odd) of the track number being tracked, the sign of the deviation amount (to which side the disc is deviated from the center) can be determined.

The operation of the circuit shown in FIG. 1 will be described below. First, a case will be described in which the desired track younger TRd is set to 10, the magnetic head has moved to the 10th track, and is now tracking. Also, in the setting device 12, =0.08,
In other words, it is assumed that the positional deviation of the magnetic head is allowed up to 8 channels of one track.

The magnetic head 3 picks up the servo information, the signal is read out by the servo information reading circuit 5, the track number detection circuit 7 reads the read track number TRa=10, and the precision position information detection circuit 8 reads the read precision position FPa=0.03. In other words, let us assume that there are three truck hits. In this case, F
Since Pa(0,03) <K(0,8), comparator 1
When the output SWc from 3 is set to 0, the position of the switch 14 shown by the broken line in FIG. 1 is selected. That is, the output of the switch 14 is FP, and this positional error FPa is amplified by the amplifier 11 and applied to the drive mechanism 4 to position the magnetic head 3 at the center of the normal track.

Next, read track number TRa = 101 read precision position FP
When a=0.1, the output swc of the comparator 13
=i, and the switch 14 is selected to the position shown by the solid line in FIG. The input terminal of the switch at the solid line position has rn, (x
o)-(rna(xo)+FpaCoJ))=-o, 1
is applied, this is amplified by the amplifier 11, and is used to adjust the position of the magnetic head 3. In this case, essentially the switch 14
is the same as in the case of the broken line, but the read track number TR
This is because a is the same as the desired track number TR. If TRa deviates to 11 or 9, an error signal is obtained to move the magnetic head 3 to the set 10 track, and the magnetic head 3 is positioned accordingly.

In addition, in the above explanation, if a large positional shift such as moving from one track to another is about to occur, the time from one servo information read to the next servo information output will be longer than the position relative to the servo. Since it is sufficiently short, it is possible to detect that the precise position error FPa has exceeded 50%, and it is possible to switch to the above-mentioned control mode that refers to the track number.

In carrying out the present invention, modifications of the outer fences described above may be adopted, for example, circuit elements 6 to 10.
12 to 14 can be realized by microprogramming.

Effects of the Invention As is clear from the above description, according to the present invention,
If the magnetic head is at an allowable track deviation position, the track deviation can be accurately corrected using precision position error, and errors caused by incorrect track younger sister reading that can occur in a method that constantly refers to the track number can be avoided. position control can be prevented. In addition, if the track deviation deviates from a predetermined limit value, the track number is also referenced to perform position control to the correct track position to prevent data from being read or written on the wrong track. can. Furthermore, such a case is considered to be extremely rare, and the conventional track number storage reliability is sufficient.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main parts of an apparatus for performing a magnetic head positioning method as an embodiment of the present invention, FIG. 2 is a diagram conceptually showing the magnetic area of a magnetic disk in the apparatus shown in FIG. 1, and FIG. The figure is a diagram explaining the magnetic information in Figure 2, and Figure 4 is a diagram explaining the magnetic information in Figure 2.
FIG. 3 is a diagram showing signal characteristics obtained from the magnetic disk shown in FIG. (Explanation of symbols) 1...Magnetic disk, 2...Spindle motor, 3
... Magnetic head, 4... Drive mechanism, 5... Servo information reading circuit, 6... Track number setting circuit, 7...
・Track number detection circuit, 8...Precise position information detection circuit, 9...Adder, 10...Subtractor, 11...Amplifier, 12...Reference position error setting circuit, 13...・Comparator, 14...switch. Patent applicant Fujitsu Ltd. Patent agent Akira Aoki Patent attorney Kazu Nishidate Patent attorney Kazuo Nishidate Patent attorney 1) Yukio Patent attorney Akira Yamaguchi

Claims (1)

[Claims] 1. A magnetic head reads servo information having a track number and precise position information stored in advance along each track on a magnetic disk medium surface, and the read servo information is negatively fed back. In the method for positioning a magnetic head in which the magnetic head is positioned on a predetermined track using If the position error is within a predetermined position error, the magnetic head is positioned based on the position error, and if the position error exceeds a predetermined position error, the magnetic head is positioned based on the track number and position error of the read servo information. A magnetic head positioning method characterized by: