JPH0480471B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a recording medium having an embedded servo pattern that allows the positioning of a head that is moved at high speed with respect to a recording medium to be performed easily and with high precision, and a recording medium that is provided with an embedded servo pattern, This invention relates to a method for positioning a head relative to a medium.

[Technical background of the invention and its problems]

Conventionally, in magnetic disk devices and the like, a servo surface servo method has been widely adopted in which the head is positioned on the data surface by reading servo information written on one surface of the disk plate. However, with this method, thermal off-track between the servo surface and the data surface is likely to occur due to the temperature gradient that occurs within the device.
The problem is that it is essentially impossible to increase the track density. Therefore, recently, a data surface servo method has been attracting attention, in which servo information is written in a defined area on the data surface of a disk plate. One of them is a so-called embedded servo system in which servo information for positioning is embedded in advance in an index sector for detecting a data sector. According to this method, it is possible to perform positioning without thermal off-track by using conventional recording media and heads as they are, and by adding a small amount of electric circuitry, and various research is being carried out.

However, with this embedded servo system, servo information indicating position information can only be obtained from the servo sector, so when the head is moved at high speed, the above servo information cannot be obtained, making it difficult to accurately move the head to its target track. The problem is that positioning is difficult. In order to solve this problem, it is possible to increase the amount of servo information, but if this is simply done, the proportion occupied by the servo sectors on the disk will increase, resulting in a significant reduction in the data recording capacity. was invited.

Conventionally, a method has been proposed in which a track number is encoded and recorded in addition to servo information for precise positioning, and the head is roughly positioned using this code. (Japanese Unexamined Patent Publication No. 51-131607) However, with this method, if the head is moved at a higher speed or if there is a small defect in the disk plate, the above track number may become unreadable. There is a problem in that it is very difficult to accurately control the speed and position. Another method is to roughly position the head by measuring the number of tracks using the servo signal track group signal when the head is moving at high speed, then switch to low speed movement and precisely position the head based on the individual servo signals. One that performs positioning has been proposed. (Japanese Unexamined Patent Publication No. 54-80719) However, with this method, when trying to increase the moving speed of the head, for example, when using a track group signal with a cycle of 8 tracks, the moving speed is detected only every 8 tracks. speed control is extremely inaccurate.
Moreover, since accurate servo information cannot be obtained until the head is moved to the desired position less than one track away, there is a drawback that the seek time of the head ends up being longer.

Another method is to make the servo information multi-phase, but as the amount of servo information increases due to this multi-phase conversion, the erasing section for detecting servo sectors also has to cover a wider area. come to need it. For this reason, the data recording area is significantly reduced. Furthermore, the electrical circuits used to decode the servo patterns for each phase described above have become more complex.
Since the processing time becomes longer, it is not practically preferable to simply increase the number of servo phases in order to increase the moving speed of the head.

[Purpose of the invention]

The present invention was made in consideration of these circumstances, and its purpose is to achieve high-speed movement of the head without significantly increasing the servo sector area and with a simple electrical processing circuit configuration. An object of the present invention is to provide a highly practical recording medium that enables accurate positioning, and a head positioning method using this recording medium.

[Summary of the invention]

The present invention provides a head positioning method in which a head is positioned on a desired track on a disk-shaped recording medium in which a predetermined servo pattern is embedded in a servo track.
It consists of an N-phase first servo pattern and a pair of pattern information whose patterns change periodically for at least every 4N adjacent servo tracks, and a part of each of these pairs of pattern information is contained within the same servo track. a first signal group consisting of at least two difference signals between signals respectively obtained from the first servo pattern via the head; , a second signal group consisting of the sum and difference signals between the first signal group, and a third signal group respectively obtained from the second servo pattern via the head, and calculate the second signal group. After detecting the existence section of the head with respect to the disk-shaped recording medium from the polarity and magnitude relationship of the groups and the value of the third signal group, at least one of the sum signal and the difference signal constituting the second signal group is used. The present invention is characterized in that the position of the head within the existing section with respect to the disk-shaped recording medium is detected, and the head is positioned on the desired track.

〔Effect of the invention〕

Therefore, according to the present invention, the first and second servo patterns can be formed in a small number of servo areas, and can be easily servo decoded. Moreover, the first and second servo patterns described above make it possible to detect the position with high precision even when the head is moving at high speed, so the speed of the head can be accurately controlled and seek can be performed in a short time. It has great practical effects, such as making it possible to carry out.

[Embodiments of the invention]

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

FIG. 1 shows the relationship between servo sectors and data sectors in an embodiment using a two-phase dive pattern as the first servo pattern.
1 indicates a data sector, and 2 indicates a servo sector. This servo sector 2 is provided with a relatively long erasing section 3 for sector detection. This erasing section 3 is constructed to have the longest erasing period in the same track. Therefore, the servo sector 2 has a clock signal extraction and
A synchronization signal 4 used as an AGC signal is embedded, and servo information 5 is also embedded. This servo information 5 includes a first servo pattern 6 consisting of a two-phase dive pattern provided with track position 4N as a reference, and a pattern period of 8 tracks, a part of which, here, 2 tracks, are superimposed. The second servo pattern 7 is composed of a second servo pattern 7. The second servo pattern 7 has partial patterns 7a and 7b.
are provided on both sides of the first servo pattern 6, thereby minimizing the area of the erasing section 3 in the servo sector 2. Note that 8 in FIG. 1 is a head for reading out these servo information.

To explain the above servo information in more detail, the first servo pattern 6 has patterns spanning two tracks arranged alternately at positions A and B, and shifted by one track from these at positions C and B. In D, they are arranged alternately. And these positions A, B,
At positions P and Q on both sides of C and D, second servo patterns spanning four tracks are arranged with a shift of two tracks. Now, if the head 8 at track position 4N+4 reads out the data in the servo sector 2, the read signal will be as shown in FIG. In other words, the amplitude is zero at position P, the amplitude is ``1/2'' at positions A and B, and
A servo signal having an amplitude of "1" at position C, zero amplitude at position D, and "1/2" amplitude at position Q is read out in correspondence with the positions.

In the servo signal shown in FIG. 2, A,
The signals indicated by B, C, and D are information indicating the position of the first servo pattern, and the difference signals X, Y (first signal group) of X=A-B Y=C-D are recorded in the head. This becomes a position signal for the medium. In order to obtain such signals X and Y, each of the signals A, B, C, and D mentioned above is sampled through a peak hold circuit, and while this is held for one sector,
Subtraction processing may be performed between each signal. A circuit that performs such processing is usually called a servo decode circuit. Also, at this time, a signal obtained from the second servo pattern 7 (third signal group)
P and Q may be used after being detected through a peak hold circuit, for example, or the presence or absence of the pulse may be detected by discrimination based on a preset level.

Therefore, position detection based on the signals X and Y detected as described above uses the second signal group U=X+Y V=X-Y, which is obtained by taking the sum and difference of the position signals X and Y. It will be done. The relationships among the signals X, Y, U, V, P, and Q obtained in this way are as shown in FIG. 3, and are regular relationships determined by the head position. However, the waveform shown in FIG. 3 shows an ideal state when the head is moved at low speed from the inner circumferential side to the outer circumferential side with respect to the recording medium. Furthermore, L ₀ , L ₁ , L ₂ , and L 3 shown in FIG. 3 are the signals X and L ₃ obtained from the first servo pattern 2.
Y, U, and V indicate head track presence sections, respectively. However, it is assumed that the 4N track is included in the section _L0 , the 4N+1 track is included in the section _L1 , the 4N+2 track is included in the section _L2 , and the 4N+3 track is included in the section _L3 .

Thus, assuming that the head is now on-tracking on the 4N track and has moved within a range of less than 4 tracks, the head position at that time can be determined using the above signals X and Y according to the processing flow shown in FIG. After performing the section detection, the position within the above-determined section can be determined with high precision using the signals U and V and following the processing flow shown in FIG. That is, as shown in FIG.
By reading Y and determining its polarity, the track sections L ₀ , L ₁ , L ₂ , and L ₃ in which the heads exist can be identified, as is clear from the signal polarity shown in FIG. Thereafter, the head position within the determined section is determined using signal U or signal V. For example, the interval
If it is determined to be L ₃ , as shown in Fig. 5, the sum signal U, which is the sum signal, is obtained from the signals X and Y, and then the amplitude of one track is set as α from the value of this signal U, and t ₃ Find the head position within the interval =0.5+U/α. After that, it is determined to which section L _B corresponds to the position of the head before the movement (the section where the head exists before the movement), and the position of the head indicated by L _B is determined according to the judgment result. The current absolute position of the head (track position on the disk) PP can be obtained by adding the inter-track movement amount and the head position _t3 to the absolute position before movement (track position on the disk) INT (PB). Become. Then, the interval L ₃ in which the head found in this way exists
This information will be set as the information L _B of the section where the determined head exists.

As described above, if the moving speed of the head is less than 4 tracks, the current position of the head on the recording medium can be accurately determined. However, if the head moves at a speed of 4 tracks or more but less than 8 tracks,
It is no longer possible to determine the current position of the head only from the first servo signal consisting of the two-phase servo pattern described above. In other words, only from the first servo pattern, four track sections L ₀ , L ₁
Although it is only possible to identify ~ _L3 , in this case, the sections a0, _{a1 to a7} , which correspond to eight tracks in which the above sections _L0 , _L1 to _L3 are repeated twice, are identified. It is necessary to identify. These intervals a ₀ , a ₁ to _{a 7}
The second servo pattern described above is used in combination to enable identification. The second servo pattern 7 will be explained again. When track sections that can be identified by N-phase servo signals are continuous, the second servo pattern 7 is configured to have a pattern period of 4N tracks in order to identify them. Furthermore, the patterns are configured so that parts of the patterns overlap in a certain track. Therefore, in the example shown in FIG. 1, the signals P and Q show waveform changes as shown in FIG. Determined interval L ₀ ,
Although _L1 to _L3 , the possible values of the signals P and Q differ depending on the head position.
By the way, if there is no overlapping part in a part of the second signal pattern, exactly the same signals P and Q will be obtained at each boundary of the pattern, so it is difficult to determine which boundary the above is. cannot be identified. Therefore, such signals P and Q
If the above-mentioned section judgment is performed using
This means that a ₀ , a ₁ to a ₇ can be identified accurately.

That is, in the example shown in FIG. 3, the signal P is 8
The track changes as one cycle, and a flat part for three tracks and a slope part for one track are repeated alternately. Therefore, except for the above-mentioned slope, it is possible to determine, for example, whether a track section is a 4N track or a 4N+4 track, based on the value of the signal P. However, at the above slope, the signal P
From the value alone, is it 4N + 2 tracks?
Or it is very difficult to judge whether it is 4N+6 tracks. In this case, if we check the value of one signal Q, we will find that its slope position is different from that of the signal P due to overlapping patterns of one or more tracks as described above.
Using the value of the signal Q, it is possible to clearly identify whether it is a 4N+2 track or a 4N+6 track.

The section determination performed by using the signals P and Q in combination as described above is performed, for example, as shown in FIG. 6. That is, after determining the sections _L0 , _L1 to _L3 , by determining the value of the signal P or signal Q, it becomes possible to determine the track sections _a0 , _a1 to _a7 . . Thereafter, in this determined interval, by determining the intra-interval head position t indicated by the signals U and V, the current absolute position PP of the head is determined in the same manner as in the process described above.

In the example shown in FIG. 1, the second servo pattern overlaps by two tracks, but if the second servo pattern overlaps by one track, the waveform of signal Q with respect to signal P will be as shown by the broken line in FIG. It will be shown as follows. Even in this case, since the position of the slope part where the section determination is ambiguous is different between the signals P and Q, it becomes possible to perform accurate section determination here.

Furthermore, if the head moves at a high speed of less than 16 tracks, a pattern 9 having a pattern period of 16 tracks as shown in FIG.
It becomes possible to accurately determine the section corresponding to 16 tracks. However, even in this case, it is necessary to overlap a portion of the pattern 9 over one or more tracks so that the slopes of the signals S and T obtained thereby do not overlap at the same track position. Furthermore, even when moving on 32 tracks, 32
A second servo pattern whose pattern period is the track may be added.

As explained above, according to the present invention, in addition to the first servo pattern consisting of N phases, the pattern period is 4N tracks or an integral multiple thereof, and a part thereof overlaps one or more tracks. By forming the second servo pattern on the recording medium, it is possible to accurately determine the head position even when the head moves at high speed. Moreover, the section determination in detecting the head position can be performed very easily and accurately, and the servo decoding circuit can also be easily configured.

In particular, regarding the expansion of the area of servo sector 2 by adding the second servo pattern mentioned above,
This can be kept sufficiently small compared to conventionally considered multi-phase servo patterns. In other words, compared to multi-phase servo patterns, the area increase rate can be reduced to about half. Therefore, the reduction in area of the data sector 1 can be reduced, and the large capacity recording performance can be maintained to some extent. Therefore, the practical advantages obtained by the method of the present invention are enormous.

Note that the present invention is not limited to the above embodiments. For example, it can be applied not only to magnetic disk devices but also to optical disk devices. Also the first
There is no need for the servo pattern to be two-phase. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of the drawing]

The figures are for explaining an embodiment of the method of the present invention, and FIG. 1 is a diagram showing an example of a servo pattern according to the embodiment, FIG. 2 is a diagram showing a readout signal waveform of the servo pattern, and FIG. Position signal X, Y, U, V,
A waveform diagram showing the relationship between P and Q, FIG. 4 is a diagram showing an example of a general section determination process, FIG. 5 is a diagram showing an example of the position detection process, and FIG. 6 is a diagram showing the section determination process in the embodiment method. FIG. 7 is a diagram showing an example of a different servo pattern. 1...Data sector, 2...Servo sector, 3
... Eraser section, 4 ... Synchronization signal, 6 ... First servo pattern, 7, 9 ... Second servo pattern,
A, B, C, D... Servo signal, X, Y... Position signal (first signal group), U, V... Third signal group,
P, Q...Second signal group (second servo signal).

Claims (1)

[Scope of Claims] 1. In a head positioning method for positioning a head on a desired track on a disk-shaped recording medium in which a predetermined servo pattern is embedded in a servo track, the servo pattern is an N-phase first servo pattern. , consists of a pair of pattern information whose patterns change periodically for at least every 4N adjacent servo tracks, and a part of each of the pair of pattern information exists in the same servo track. a first signal group consisting of at least two difference signals between the signals respectively obtained from the first servo pattern via the head; a second signal group consisting of sum and difference signals;
A third signal group obtained from the second servo pattern through the head is determined, and from the polarity and magnitude relationship of the second signal group and the value of the third signal group, After detecting the existing section of the head, detecting the position of the head within the existing section with respect to the disk-shaped recording medium using at least one of the sum signal and the difference signal constituting the second signal group; A head positioning method characterized in that the head is positioned on a desired track. 2. The head positioning method according to claim 1, wherein the pair of pattern information constituting the second servo pattern is embedded and formed on both sides of the first servo pattern. 3. The head positioning system according to claim 1, wherein the first and second servo patterns are embedded in servo tracks in servo sectors provided between data sectors.