JPS63298782A - Head position control method - Google Patents

Abstract

PURPOSE:To attain sure control by detecting a 1st servo information so as to correct the position deviation of a head with respect to a track and detecting a 2nd servo information so as to correct the position of the head in the unit of tracks so as to widen the locking limit of the servo. CONSTITUTION:After reading a data of a sector N in a data sector 4, a head reproduces simultaneously burst signals 5, 6, frequency components f1, f2 of the burst signals 5, 6 are discriminated by a discrimination circuit and if either signal exists, an amplitude sampling signal of a servo burst signal is generated by the circuit constitution. Then the head of the servo pattern is detected by utilizing the ease and sureness of the detection of a 1st pattern as the simultaneous reproduction of two kinds of frequency signals, and the degree of freedom of a 2nd pattern constitution is utilized to widen the servo locking limit. Thus, the head position deviation is surely detected and the head position control with wide servo locking limit is attained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a head position control method using a tracking servo device that tracks the head by detecting servo information formed on the recording surface of a recording medium. be.

[Prior Art] Conventionally, when recording and reproducing on high-density recording media such as magnetic disk drives, in order to accurately trace the head to the track, it has been necessary to correct the misalignment between the head and the track on the recording medium. A tracking method is used that detects servo information recorded on the head and corrects the head position.

A first example of a pattern of servo information on a recording medium in such a conventional tracking method is shown in FIG. 5. FIG. 5 shows a servo pattern using two types of frequency signals (hereinafter referred to as (referred to as dual frequency servo pattern)
As shown in the figure, servo patterns 2 and 3 are recorded before each data sector 1, shifted by half a track pitch. Servo patterns 2.3 have different frequencies fl
+f2 burst signal, which is simultaneously reproduced by the heads running on the track. A frequency discrimination circuit separates this into an f1 component signal and an f2 component signal, and by controlling the head positioning mechanism so that the component ratio is 1, the head is always accurately positioned on the track. It is something.

Further, FIG. 6 shows another example of a conventional tracking servo pattern, and shows an example of a so-called staggered burst type servo pattern. In the same figure, A
, B are mutually different pulse trains having pulses with different pulse intervals such as 1 times, 2 times, 2.5 times the bit interval T.

Further, C, D, E, and F are usually burst signals of the same frequency. For pulse trains A and H, pulse intervals are measured and discrimination can be made based on how many pulse intervals of which length there are. After detecting at least one pulse train A or B of the pulse trains A and H, a timing signal for sampling burst signals C, D, E, and F for servo control is generated, and the burst signals C,
D.

Measure the amplitude of each reproduced signal E and F.

The head positioning mechanism is controlled based on the measured amplitude ratio of each reproduced signal.

[Problem that HA +51 attempts to solve] As mentioned above, in the first example of the conventional servo pattern, the same servo pattern is repeated every two tracks, so the servo pull-in limit is less than ±1 track. The problem was that it was narrow.

In addition, in the second example of the conventional servo pattern, the same servo pattern is repeated every four tracks, so the servo pull-in limit can be set as wide as ±2 tracks.
When discriminating B, it is necessary to accurately discriminate relatively close pulse intervals such as 1, 2, and 2.5 times the bit interval T, and reliable operation is difficult under the influence of noise etc. There was a problem.

The present invention has been made to solve these conventional problems, and provides a tracking servo pattern that has a wide servo pull-in limit and can perform reliable control, and furthermore provides a tracking servo pattern for tracking a recording medium using this pattern. The purpose is to provide a method).

[Means for Solving the Problems] In order to achieve the above object, the first aspect of the present invention is to detect servo information recorded in relation to a recording track on a recording medium and perform recording on a head. A head position control method for controlling the position of a track, the method detecting first servo information formed by alternately forming frequency signals different from each other in the direction in which the tracks are arranged, spanning the adjacent recording tracks. The positional deviation of the head relative to the track is corrected so that the levels of the frequency signals are equal, and n
(n>2) The second
The second invention detects servo information recorded on a recording medium to correct the position of the head in track units. A method for detecting the amount of positional deviation with respect to a recording track, the method detecting the amount of positional deviation of the head with respect to the opposing track by detecting first servo information formed by alternately forming different frequency signals in the direction in which the recording tracks are lined up. At the same time, the amount of positional deviation of the head in units of tracks is detected from second servo information that is different between adjacent tracks and is formed repeatedly at n (n>2) track periods.

[Function] With the above configuration, the servo pattern can be detected by utilizing the ease and reliability of detecting the first pattern in which signals of two types of frequencies are simultaneously reproduced by the head running on the track. Detecting the leading position and further utilizing the degree of freedom in the configuration of the second pattern to widen the servo pull-in limit became the turning process.

[Embodiment] FIG. 1 shows a first example of an embodiment of the present invention, in which 4 is a data sector, 5 is a burst signal of frequency f1, and 6 is a frequency f1.
2 burst signals, G and H.

I and J are servo control burst signals (hereinafter referred to as servo burst signals) having the same frequency.

In the above configuration, let us now consider the case where the head runs on track 4n+2. After reading the data in sector N in data sector 4, the head simultaneously reproduces burst signal 5.6 and frequency components 1 . f
The circuit is configured to discriminate t using a discrimination circuit, and generate an amplitude sampling signal of the servo burst signal if either signal is present.Here, the frequency fl.

The reason why signals of different frequencies f2 are used is that if the same frequency were used, the signals would cancel each other out due to the phase shift, making detection by the discrimination circuit unstable and unstable. Also, since the frequency of f,,f, is selected to be different (usually lower) than the data recording frequency, the amplitude sampling signal of the servo burst signal, which will not be mistakenly detected in the data sector 4, is the same as the servo burst signal. G, H, I,
It is generated a total of four times, once for each signal of J. Servo burst signals G, H, and I are synchronized with the amplitude sampling signal of the servo burst signal.

Measure the amplitude of J. Now, servo burst signals G, H
is not detected, servo burst signals I and J are detected,
Control is performed so that the amplitudes of the servo burst signals I and J are equal. For example, if +1) rack off-track occurs, the amplitudes of the servo burst signals G and J are controlled to be equal.
are detected with the same amplitude, so it can be determined that there is an off-track of +1 track. Considering the case where an off-track of +2 track occurs in the 0th order, the servo burst signals G and H are detected with the same amplitude. . However, this
Since this is equivalent to the case where off-track of -2 tracks occurs, it becomes impossible to determine the amount of off-track. Therefore, the pull-in limit of the servo control in the embodiment shown in Fig. 1 is +2 tracks, which is equivalent to the second conventional example, but the advantage is that the beginning of the servo signal can be reliably detected by the dual-frequency servo pattern detection. There is.

FIG. 2 shows a second example of the embodiment, where 7 is a data sector;
8 is a burst signal with a frequency f, which is longer in time than the burst signal 5 shown in FIG. By making the first burst signal 8.9 longer in time, it is possible to apply the same servo system as in the conventional example shown in FIG. can also be applied. In other words, this servo pattern has the advantage of being compatible with the two servo methods.

In the configuration shown in Figure 2, the head is now track 4n+
2, after reading the data in data sector N, the head simultaneously reproduces burst signals 8 and 9, uses a discrimination circuit to discriminate between the frequency components of burst signals 8 and 9, and f2, and selects one of them. If the signal is present, an amplitude sampling signal of the servo burst signal is generated. In this case, the servo burst signal M is synchronized with the amplitude sampling signal.

N is detected, and the amplitudes of the servo burst signals M and N are controlled to be equal.

Furthermore, as a modification of the embodiment in FIG. 2, although not shown, one of the burst signals 8 and 9 and the servo burst signals in FIG. It is conceivable to place it in In addition, the servo system of the first conventional example and the first embodiment are applied simultaneously.

According to this method, the linearity of the detected track position error signal can be improved. In this case, the accuracy of the 1-position error amount decreases because the burst signal 9 is not reproduced. However, according to this method, even in this state, two of L, M, and N are always detected in the servo burst signal, and the position error amount can be accurately detected.

FIG. 3 shows a third example of the embodiment, in which 10 is a data sector, i
f is a burst signal of frequency f1, 12 is a burst signal of frequency f2, and burst signals 11 and 12 are burst signals 1 having the same time length as burst signals 8 and 9 in FIG.
3 and 14 are short burst signals of frequency f and 1
Both are placed temporally apart. The burst signals 15 and 16 are short burst signals having a frequency f and are arranged temporally apart.

Consider the case where the head runs on track 4n+2 with the above configuration. After reading the data in sector N of data sector lO, the head uses a discrimination circuit to discriminate between the frequency component signals of 0 frequency f1 and fO, which simultaneously reproduce burst signals 11 and 12, and if either signal exists, the amplitude The circuit is configured to generate a sampling signal, the amplitude sampling signal is generated three times, and the first signal is the first signal.

After discrimination, the amplitudes of the signals at frequencies ftT& and ttr& are measured simultaneously. The next two times are at frequency f.

Only the presence of the frequency f22-order signal is detected. In this case, the f, component signal and the f2r& signal are measured to have the same amplitude, and subsequently, the f,-component signal is detected twice. For example, if we consider the case where an off-track of +1 track occurs, first a signal of frequency ftrIt and a signal of frequency f22nd order are detected with the same amplitude, but then a signal of frequency f11th order is detected, and finally frequency f2
Since a second-order signal is detected, it can be determined that there is an off-track of +1 track.Considering the case where an off-track of +2 track occurs in the 0-order, first, the frequency fit signal and the frequency f22-order signal have the same amplitude. Then, a signal of one frequency fl component is detected twice. This is -
Since this is equivalent to the case where there are two off-tracks, it becomes impossible to determine the amount of off-track. Therefore, the servo pull-in limit is +2 tracks, which is the same as the conventional example shown in FIG. 6, but the time length of the servo signal can be shortened and reliable operation can be performed.

In the fourth example of the embodiment, the time lengths of the burst signals 13, 14, 15, and 16 in the embodiment of FIG.
The time length is approximately the same as 1.12. This makes it possible to measure the amplitudes of all burst signals.The set of zero-order first burst signals and the second set of burst signals. Either one of the third burst signal sets is placed on the track centerline.

Figure 4 is 2. This is a case where the third burst signal is placed on the track center line.

In the configuration shown in Figure 4, the head is now on track 4n+.
2, an amplitude sampling signal is created in the same manner as in the embodiment shown in FIG. 3, and the amplitudes of the burst signals 18° and 19 are measured using the first amplitude sampling signal to obtain measured values of the same amplitude.

The convergence of the burst signal 22 is measured using the second amplitude sampling signal, and it is found that the signal has a frequency f. In the third amplitude sampling signal, no burst signal is measured. In other words, the detection of a signal with frequency f88 in the second amplitude sampling signal indicates that the head is running near track 4n+2. The amplitude ratio of the burst signal 18.19 measured with the first amplitude sampling signal gives the position error.

For example, +1) If we consider the case where rack off-track occurs, after first measuring the amplitude of the burst signal 18.19, no burst signal is measured in the second amplitude sampling signal, and in the third The amplitude of the burst signal 23 is measured with the amplitude sampling signal of f2
It can be seen that the signal is From this, it can be determined that there is an off-track of +1 track.If there is an off-track of +2 track in the 0th order, the frequency f and acid component signal are detected in the second amplitude sampling signal, and the acid component signal is detected in the third amplitude sampling signal. Nothing is detected in the signal, which means
Since this is equivalent to the case where there is an off-track of -2 tracks, the servo pull-in limit is +2 tracks. The advantage of this pattern is that the linearity of the position error signal can be ensured.For example, consider the case where there is an off-track of approximately +0.5 tracks from track 4n+2.

With the first amplitude sampling signal, only the burst signal 19 can be sampled, and it is not possible to calculate an accurate off-track amount with this alone.However, the amplitude of the burst signal 22 can be sampled with the second amplitude sampling signal, and the burst signal Since the amplitudes of the burst signals 22 and 23 are measured, the off-track amount can be accurately calculated based on the amplitude ratio of the burst signals 22 and 23.

[Effects of the Invention] As explained above, according to the head position m control method of the present invention, the first recording track is formed by alternately forming different frequency signals across the adjacent recording tracks and in the direction in which the tracks are lined up. servo information is detected and the positional deviation of the head relative to the track is corrected so that the level of each frequency signal is equalized, and second servo information that is repeatedly formed at n(n>2)) rack periods is detected. correcting the position of the head on a track-by-track basis, or detecting first servo information formed by alternately forming different frequency signals in the direction in which the recording tracks are arranged, and detecting the amount of positional deviation of the head with respect to the opposing track. In addition to detecting pHI
mutually different between adjacent tracks, and n (n>2))
By detecting the amount of positional deviation of the head in units of tracks from the second servo information that is repeatedly formed in a rack cycle, it is possible to reliably detect the amount of head positional deviation and to control the head position with a wide servo retraction limit. becomes.

[Brief explanation of drawings]

Fig. 1 is a diagram of a servo pattern showing a first example of an embodiment of the present invention, Fig. 2 is a diagram of a servo pattern showing a second example of the embodiment, and Fig. 3 is a diagram of a servo pattern showing a third example of the embodiment. FIG. 4 is a diagram showing a servo pattern showing an example of tfS4 according to an embodiment of the present invention, and FIGS. 5 and 6 are diagrams showing conventional servo patterns. Agent Patent Attorney 1) Haru Kitatake Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1) A head position control method for controlling the position of a head with respect to a recording track by detecting servo information recorded in relation to a recording track on a recording medium, the method comprising: detecting first servo information formed by alternately forming different frequency signals in the direction in which the signals are lined up, and correcting the positional deviation of the head with respect to the track so that the levels of each frequency signal are equal;
A head position control method, comprising: correcting the position of the head in track units by detecting second servo information repeatedly formed at n (n>2) track periods. (2) A method of detecting the amount of positional deviation of the head with respect to the recording track by detecting servo information recorded in relation to the recording track on the recording medium, in which signals of different frequencies are alternately transmitted in the direction in which the recording tracks are arranged. The positional deviation amount of the head with respect to the opposing track is detected by detecting the first servo information formed in the first servo information, and the first servo information formed in A method for detecting an amount of head positional deviation, characterized in that the amount of positional deviation of the head in track units is detected from second servo information.