JPH0416872B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a head positioning method that enables highly accurate head positioning by reading out servo signals embedded in a recording medium.

[Technical background of the invention]

Conventionally, in magnetic disk devices and the like, a servo surface servo system has been widely adopted in which servo information written on one surface of a disk plate is read and the head is positioned on the data surface of the disk plate. However, this method has the problem that thermal off-track tends to occur between the servo surface and the data surface due to the temperature gradient occurring within the device, and it is essentially impossible to increase the track density. Recently, therefore, data surface servo systems, called embedded servo, have been attracting attention, in which servo information is written or embedded in a defined area on the data surface of the disk plate to control the position of the head. I'm getting used to it. According to this method, the head can be positioned without causing thermal off-track problems by using conventional recording media and heads as they are, and by adding a small amount of electrical circuitry. Furthermore, since the ratio of servo sectors to data sectors is generally as small as 10% or less, it is particularly suitable for devices with one or two disk plates and devices with so-called cartridge type disk plates.

However, in this servo system, since the servo information for detecting the head position can only be obtained from the servo sector, a situation arises in which the servo information cannot be obtained when the head is moved at high speed. At this time, a problem arises in that it becomes difficult to accurately position the head on the target track. In order to deal with this, the present inventors used a multiphase servo pattern as servo information, and the first signal group obtained by this and the second signal group obtained by calculating the sum and difference between the signal groups. A method is provided in which the track section in which the head exists is determined using the second signal group, and the current position of the head relative to the disk plate is detected with high precision from the head position within the track section obtained from the second signal group. proposed earlier.

That is, as illustrated in FIG. 1, a data sector 1 and a servo sector 2 are provided on the disk board, and a two-phase deformation dibit pattern 3 and a synchronization signal 4 for the clock and AGC signals are embedded in the servo sector 2, respectively. The head 5 reads these signals 3 and 4 to detect the position. At this time, 5a, 5b, 5c, 5d
When the head 5 is located at the position shown in FIG.
The results are as shown in d. In FIG. 2, S indicates a synchronizing signal waveform, and A, B, C, and D each indicate a signal position for position detection.

Now, however, position signals X and Y are obtained as the first signal group from the signals read out as described above, as X=A-B Y=C-D, and are composed of the sum and difference of these signals X and Y. When the second signal group U=X+Y V=X-Y is obtained, these signals X, Y, U,
V changes as shown in FIG. 3 depending on the head position. Therefore, by determining whether the signals X and Y are positive, negative, or zero, the track sections L ₀ , L ₁ , L ₂ ,
It is possible to accurately obtain L ₃ and further calculate the head position in this determined section from the values of signals U and V that change linearly in that section, for example, t ₀ =V/a+0.5. Since the current position of the head can be accurately determined by adding the known position of the head before movement, it is possible to accurately detect the current position of the head. However, in the above formula, t ₀ indicates the position in the section L ₀ , a is the amplitude of the signal X,
In other words, it corresponds to the track width.

Thus, by using the current position information of the head that is simply and accurately detected as described above, the head can be accurately positioned with respect to the target track by controlling the moving speed and position of the head. becomes possible.

[Problems with background technology]

However, the core width of a head is generally set narrower than the track pitch of a disk in order to avoid data overwrite modulation. That is, while the servo pattern recorded in the servo sector is recorded to the full extent of the track pitch, data recording and reproduction in the data sector is performed using a head having a core width narrower than the track pitch. Therefore, the first signal group, that is, the position signals X, Y, obtained from the servo signals read using the narrow core width head
As shown in Figure 4, the flat part is long,
As a result, the signals U and V obtained by calculating the sum and difference of these signals X and Y will no longer be linear in the region corresponding to the determined section.
In other words, as shown in FIG. 4, the signal is a signal that shows a level change having a stepped portion. For this reason, if the position detection process shown by the above-mentioned formula is performed as is, a large error will occur, resulting in a problem that accurate positioning control cannot be performed. Furthermore, depending on the signal state, there is a possibility that position detection may not be possible over a certain position range at the stepped portion where the level is 0, that is, an undetectable zone may occur.

[Purpose of the invention]

The present invention was made in consideration of these circumstances, and its purpose is to position the head quickly and accurately even when using a head with a core width narrower than the track pitch. It is an object of the present invention to provide a highly practical head positioning system that can be used.

[Summary of the invention]

The present invention uses a first signal group (position signal) obtained from a plurality of phase servo patterns of a recording medium and a second signal group obtained by calculating the sum and difference between these first signal groups. When determining the track section in which the head exists and further determining the head position in this track section, for example, a table is used or non-linear processing is performed so that the change in the second signal group in the track section is linear. The corrected signal is then used to perform position detection.

〔Effect of the invention〕

Thus, according to the present invention, even if the core width of the head is narrower than the track pitch, it is possible to always position the head accurately and at high speed, and this can be achieved with only simple signal processing. obtain. Therefore, it has a great practical effect.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The present invention provides a servo sector 2 as shown in FIG.
A servo pattern embedded in the servo pattern is read out, position signals X and Y are obtained as a first signal group from the servo signals, and a second signal group is obtained by calculating the sum and difference of these signals X and Y. When determining the track section in which the head exists and the head position in that track section from these signals X, Y, U, V, the changes in the second signal group U, V in each track section are This is to correct it so that it is almost a straight line. In other words, the head is an interval
If it exists in L ₀ , the signal V in this interval L ₀
As shown by the solid line in FIG. 5, the change in the curve has a large curvature. The value ν of the signal V in the interval L ₀ is given as a function of the head position t ₀ as shown by ν=f(t ₀ ). However, this function f is not a linear function like when the core width of the head and the track pitch are equal. Therefore, in order to correct this relationship linearly, that is, as a linear function, when the signal that is originally desired is used, the following correction calculation should be performed: =αf ^-1 (ν). However, α is an appropriate coefficient. If such correction processing is performed, the signal for position detection becomes a straight line in the section _L0 , as shown by the broken line in FIG. 5, and it becomes possible to perform accurate position detection there.

Therefore, now the signal U, which is obtained from the signals X and Y, is
Focusing on the curved portion in each track section of the V, it is considered that the degree of the curve is approximately determined by the relationship between the core width of the head and the track pitch. Therefore, a function f indicating the relationship between the head position _t0 and the signal value ν is estimated from the relationship between the core width of the head and the track pitch determined by the specifications, and its inverse function f ^-1 is used as the correction function. In this case, it is possible to correct the curvature of the signal V and straighten the signal change within the section.

Another method is to actually move the head on the track and measure the values of the signals U and V obtained thereby and the head position at this time using another measurement method, such as a laser interferometer. Create a correspondence table with the measured values. Thereafter, the curve can be corrected by correspondingly converting the values of U and V obtained from the servo pattern using this correspondence table.

FIG. 6 is a schematic configuration diagram of a magnetic disk device to which the embodiment method of creating the above-mentioned table, correcting the signal, and controlling the position of the head is applied. In the figure, reference numeral 10 denotes a rotating recording medium such as a floppy magnetic disk, on which servo patterns are embedded in servo sectors provided in predetermined areas on the data surface as shown in FIG. The rotating recording medium 10 is rotated at a predetermined speed by a drive mechanism (not shown). However, for this recording medium 10,
A head 11 supported by an actuator mechanism 17, which will be described later, is provided so as to be controlled to move in a direction perpendicular to the track. The actuator mechanism 17 is controlled to position the head 11 with respect to the rotating recording medium 10.

Thus, the servo signal read from the servo sector of the recording medium 10 by the head 11 is passed through the buffer amplifier 12 to the peak hold circuit 13a,
13b, 13c, and 13d. These peak hold circuits 13a, 13b, 13c, 1
3d is timing-controlled by a microcomputer 20, which will be described later, to detect the peak values of the servo signals at each position detection timing A, B, C, and D, respectively. That is, the servo signals are servo-decoded by these peak hold circuits 13a, 13b, 13c, and 13d. These peak hold circuits 13a, 13b, 13
A differential amplifier 14 receives the output signals of c and 13d.
a and 14b obtain the aforementioned position signals X and Y, respectively, as the difference between each signal. In other words,
The differential amplifier 14a obtains a position signal X such that X=A−B, and the differential amplifier 14b obtains a position signal Y such that Y=C−D. These signals X and Y are alternately selected via an analog switch 15, converted into digital signals by an A/D converter 16, and then sent to the microcomputer 2.
It is read as 0. Further, the position information of the head 11 determined by the actuator mechanism 17 is inputted from the buffer amplifier 18 to the microcomputer 20 via the A/D converter 19. The positional information of the head 11 obtained by the actuator mechanism 17 is obtained with high precision using an optical micro-distance measuring device or the like.

The microcomputer 20 obtains the signal information, generates the signals U and V from the position signals X and Y, and determines the correspondence between the signals based on the signal from the actuator mechanism 17 corresponding to the signal values. Create a correction table and record it. Note that this correction table may be created when the apparatus is started up. Thereafter, the microcomputer 20 executes positioning control of the head 11 with respect to the recording medium according to a control flow, an example of which is shown in FIG.

When the microcomputer 20 is given a seek command, it first calculates the distance (number of tracks) to the target track from the current head position and the set target track information, and also calculates the direction of movement of the head with respect to the target track. Determine. Depending on the determined direction, a positive or negative current necessary for moving the head is supplied to the actuator mechanism 17 via a D/A converter, and its control mode is set to speed control.

When the servo sector 2 is detected by the head 11 in this state, position signals X and Y obtained from the servo signals are read respectively. Then, by determining whether these signals X and Y are positive, negative, or zero, the track section _L0 to _L3 in which the head 11 is located is detected. after that,
The signals U and V are determined from the position signals X and Y in accordance with the determined section, and the signals U and V are corrected using the previously determined correction table, so that the signal changes within the section are linear. I will make it happen. Then, using this corrected signal, the head position within the above section is determined, and the current position of the head 11 with respect to the recording medium 10 is determined from the information on the determined section and the information on the head position before movement. .

Then, from the current position of the head 11 and the target track information obtained in this way,
Calculate the distance (number of tracks) to the target track,
It is determined whether the distance is within a predetermined range, for example less than 0.5 tracks. and,
If the distance is more than 0.5 track,
The moving speed of the head 11 is determined from the change in the head position, and the moving speed is appropriately controlled to match the target speed, and the detection of the current position of the head 11 is repeated.

In this way, when the current position of the head reaches a position within 0.5 tracks with respect to the target track, the control mode is switched to position control, and the position signals X and Y are used to control the head 11 in that track section. Position. This allows the head 11 to be accurately positioned with respect to the target track.

As described above, according to the method of the present invention, even if the core width of the head is narrower than the track pitch, and therefore the signal for position detection has a curved part in the determination section, Since this is used for positioning after linearization correction in the determined section, the head 11 can always be accurately and stably positioned. Moreover, by using a multiphase servo pattern, the above-mentioned accurate positioning can be easily performed while moving the head at high speed, and its practical advantages are enormous.

Note that the present invention is not limited to the above embodiments. For example, it is possible to use a pattern with two or more phases as the servo pattern, and the signal correction function may also be determined by another means. Also, signal X,
Y itself may be corrected, thereby linearizing the signals U and V in the section _L0 to _L3 .
In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of drawings]

Figure 1 shows an example of a servo pattern, Figure 2 shows an example of a servo pattern.
Figures a to d show the readout servo signals corresponding to the head position, Figure 3 shows the position signals X, Y and second signals U, V determined from the servo signals, and Figure 4 shows the core of the head. A waveform diagram of the signals X, Y, U, and V obtained when the width is narrower than the track pitch, FIG. 5 is a signal diagram for explaining the principle of the method of the present invention, and FIG. 6 is a diagram of an embodiment of the method of the present invention. FIG. 7, which is a schematic configuration diagram of the applied magnetic disk device, is a diagram showing an example of the processing flow of positioning control. 10... Recording medium, 11... Head, 13a, 13
b, 13c, 13d...Peak hold circuit, 14
a, 14b... Differential amplifier, 17... Actuator mechanism, 20... Microcomputer, X, Y... First signal group (position signal), U, V... Second signal group.

Claims (1)

[Claims] 1. N embedded in a predetermined area on a recording medium
A first signal group obtained by reading out the phase servo pattern by the head and a second signal group obtained by calculating the sum and difference between these first signal groups are used to read out the phase servo pattern on the recording medium of the head. When positioning the head by detecting an existing section for the existing section and detecting the current position of the head in this existing section using the second signal group, the signal of the second signal group corresponding to the existing section is detected. A head positioning method characterized by determining the current position of the head after correcting the change so that it is approximately linear. 2. The linear correction of the signal change of the second signal group in each existing interval is performed by performing nonlinear arithmetic processing when obtaining the second signal group from the first signal group. The head positioning method described in item 1. 3 Linear correction of the signal change of the second signal group in each existing section is performed using a correspondence table in which the relationship between the signal value obtained from the servo pattern and the actually measured head position when the head is moved is registered in advance. A method for positioning a head according to claim 1, which is made by reference.