JPH01271981A - Tracking controller - Google Patents

Abstract

PURPOSE:To improve accuracy in tracking control by interpolating tracking error relational data at defective position from other tracking error relational data in sectors based on a servo signal before and after a defective sector even when a defect occurs in the servo signal. CONSTITUTION:A detecting part for tracking error data is composed of an envelope detecting circuit 13 through a multiplier 19. The error data and an output from a head position detecting circuit 20 are added at an adder 21, and the added result is stored in a storing means 22 as the tracking error relational data. The defect in the servo signal is detected at a defect detecting circuit 31, delayed for one cycle at a delay circuit 34, and outputted, and the output closes a switch 33. Further, defective data in the applicable sector in the shift register of the storing means 22 are interpolated at an interpolating circuit 32 based on the tracking error relational data in the sectors before and after the applicable sector. Namely, average interpolation for obtaining the average of the data in the sectors before and after the defective sector is executed at the circuit 22, and the average is used for controlling a head position after one cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a tracking control device that performs tracking by finely controlling a head based on servo signals reproduced from a disk.

B9 Summary of the Invention The present invention provides a tracking control device that performs head tracking according to tracking error data based on a servo signal reproduced from a disk. In this case, tracking error data corresponding to the defective servo signal is interpolated from other normal tracking error data and used to perform accurate tracking.

C1 Prior Art In order to increase the recording density of disk-shaped recording media, especially to achieve high track density, it is necessary to improve the tracking accuracy of the recording/reproducing head.
When tracking is performed using general open loop control,
Since the S/N ratio may deteriorate due to off-track, or there may be a problem in reproducing adjacent tracks, a tracking servo signal is recorded on the disk-shaped recording medium in advance, and the head tracking operation is performed using a so-called closed-loop servo. It is proposed that

FIG. 4 shows an example of a recording format in which the above-mentioned tracking servo signals are recorded in advance on the flexible magnetic disk 1 (so-called floppy disk). In FIG. 4, the flexible magnetic disk 1 has a servo area S where the servo signal is recorded, and a data area where the data of -1 is recorded, along the rotational direction of the disk (direction of arrow R). The strips are arranged alternately. The center of each recording track T on which the data recording pattern 3 of data area 1jJD is recorded (dashed line in the figure) is located at a predetermined pitch p in the disk radial direction (direction of arrow A), and a plurality of tracks are arranged concentrically. The servo signal recording patterns 2 (specifically, 2. and 21D as described later) in the servo area S are such that the center of the pattern 2 is in the direction of arrow A with respect to the center of the data recording track T. ni half pitch (p/2)
It is recorded in advance so that it is disposed at a position shifted by a certain amount.

In this case, the head that scans the recording track T simultaneously scans the pair of servo signal recording patterns 2, which are disposed shifted by half a pitch on both sides with respect to the recording track T, by approximately half the width. Tracking position information is obtained according to the reproduction level ratio of the servo signal.

Here, each servo area S in the figure has an ID signal pattern 28. at the top position for identifying the servo area. is recorded and formed, and a servo burst signal pattern 2s is recorded and formed following the stiff servo 10 signal pattern 2□. This servo burst signal pattern 2. are formed such that their positions in the head scanning direction are shifted from each other at two-track periods, so that the direction of track shift of the head can be determined. Furthermore, a sector ID signal pattern 4 for identifying the sector of the data area is recorded and formed at the beginning position of the data recording area.

The recording pattern 3.4 in the data area has a recording width W which is shorter than the track pitch p, and a gap, a so-called guard band, is provided between it and the recording pattern 3.4 in the adjacent track. , prevents adverse effects such as crosstalk. On the other hand, for the servo signal recording pattern 2 (2, and 2) in the servo area S, the recording width is shorter than the track pitch p (and the adjacent recording pattern 2 in the disk radial direction (arrow A direction) If a gap is provided between the servo signal recording pattern P and
The recording width W is approximately equal to or greater than the track pitch p.

Here, the above-mentioned magnetic disk 1 is, for example, a 3.5-inch type floppy disk having a metal hub (core metal) 6 at the center, and data of several Mbytes to more than 10 Mbytes can be stored on this disk. It is assumed that recording is possible. When accessing a desired track on a floppy disk on which such servo signals are pre-recorded, the recording/reproducing head is first moved to the vicinity of the target track with relatively coarse precision using only mechanical precision (coarse movement). let me,
Next, at least two stages of control operations are performed, including accurate positioning on the target track and tracking control. The former operation is a mechanical control operation of the head movement distance using a coarse movement mechanism such as a normal floppy disk head feeding mechanism, and is called oven loop control, whereas the latter operation is a high-precision positioning and tracking operation. The operation is performed by so-called closed-loop control in which tracking servo information as described above is read and the head is minutely controlled in accordance with the servo information. Therefore, by combining these, for example, from 240 tracks to 320 tracks per side of the disc.
This allows the magnetic head to track a track or more trunks.

D1 Problem to be Solved by the Invention By the way, when a plurality of servo areas S are provided per track and the number increases, a defect may occur in at least one area during playback. Even if the floppy disk is normal at the time the signal is recorded, since the floppy disk is removable, it is easy for dust and the like to adhere to it, and data may be written in the servo area by mistake. For this reason, write protection is applied to prevent data from being written to the area where the servo signal is detected on the disk drive side, etc. However, even if there is a small probability that the servo signal is If a defect or the like occurs, there is a possibility that tracking will be disturbed from that point on, making it impossible to effectively access several peripheral sectors, or in the worst case, making the entire track unusable.

The present invention has been made in view of the above-mentioned circumstances, and is intended to be used when a defect occurs in at least one servo signal when reproducing a disc in which a plurality of servo information is recorded per track. Another object of the present invention is to provide a tracking control device that does not adversely affect tracking control.

Means for Solving the Problem The tracking control device according to the present invention, in order to solve the above-mentioned problem, at least reproduces a plurality of servo signals recorded and formed discretely along the rotational direction of the disk. a defect detection means for detecting the presence or absence of a defect in the servo signal reproduced from the disk by the reproduction head; a tracking error detection unit that detects the tracking error of the tracking error; a storage unit that stores data related to the tracking error data from the tracking error detection unit; and a storage unit that stores data related to the tracking error data from the tracking error detection unit; The apparatus comprises interpolation means for interpolating tracking error related data corresponding to the detected servo signal, and means for tracking control of the head according to the tracking error related data obtained from the storage means and the interpolation means. It is characterized by

Even if a defect occurs in the F0 action servo signal, the tracking error related data at the defective position can be interpolated from the tracking error related data based on the servo signals of other sectors, such as the sectors before and after the defective sector, allowing highly accurate tracking control. realizable.

G. Embodiment FIG. 1 is a block circuit diagram showing a schematic configuration of a tracking control device which is an embodiment of the present invention, and is similar to the tracking control device previously proposed by the inventor in Japanese Patent Application No. 62-276877. An example to which the present invention is applied is shown. FIG. 2 schematically shows the track direction of a floppy disk having the recording format shown in FIG. and servo burst signal pattern 2. is recorded and formed, and data recording pattern 3 and sector ID signal pattern 4 are recorded in the data area.
As explained in conjunction with FIG. 4, this is recorded.

In FIG. 1, a reproduction signal from a magnetic head 11 is amplified and filtered in a recording/reproduction amplifier 12, and then sent to an envelope detection circuit 13 and a servo 10 detection circuit 14. In this case, the output signal waveform from the envelope detection circuit 13 near the servo area S in the recording format shown in FIG. 2 appears as an envelope waveform EN in FIG. It is sent to container 15. Regarding the output signal SID from the servo TD detection circuit 14, as shown in FIG. 2, when the servo ID signal pattern 21D is detected, the pulse P! The ID is output and sent to the timing control circuit 16. The timing control circuit 16 uses this servo! Based on the D detection pulse P $111, the magnetic head detects the servo burst signal pattern 2. A sampling pulse is sent to the A/D converter 15 at the timing of scanning the envelope waveform EN, and the level L1 of the envelope waveform EN is
, Lt are sampled and latched into the latch circuit 17.

Each level L, , L, from the launch circuit 17 is a subtracter 1.
8 and subtraction is performed to obtain head tracking error data L+Lx. However, the tracking error data in actual servo operation is the one obtained by multiplying the output from the subtracter 18 by the coefficient a in the multiplier 19, that is, the error data a(Ll
Lz) is used.

Therefore, the configuration from the envelope detection circuit 13 to the multiplier 19 can be viewed as a tracking error data detection section.

Error data a from such a tracking error detection section
(LIL is added to the output yp from the head position detection circuit 20 in the adder 21, and the added output a(L+
Lx)+hdp, and this addition output is sent to the storage means 22 and stored as tracking error related data. This tracking error related data is updated for each sector to which the servo signal is output. Storage means 2
2 is for reading out the stored tracking error related data with a delay of one revolution of the disk rotation, and for ease of explanation, it is a shift register with the number of stages equal to the number of sectors in one revolution. . The output from the storage means 22 becomes the above-mentioned addition output (tracking error related data) for the previous sector one round before, and this is sent to the comparator 23 and output from the head position detection circuit 20. compared to hdp. The output from this comparator 23 is sent to the phase control circuit 24 of the tracking servo system.
The signal is sent to the tracking fine movement control circuit 25 via. The tracking fine movement control circuit 25 is for driving and controlling an actuator (a stepping motor, a linear pulse smoke, etc.) that finely moves the magnetic heald 11 in the disk radial direction.

Furthermore, as a main part of the embodiment of the present invention, the latch circuit 1
a defect detection circuit 31 for detecting the presence or absence of a defect in the servo signal based on the output from 7; and the storage means 22.
an interpolation circuit for interpolating data in another predetermined stage (for example, the second stage) based on the tracking error related data that is the storage content of the predetermined stage (for example, the first stage and the third stage) of the shift register; 32, and the interpolation output from the interpolation circuit 32 is sent to the other predetermined stage (second stage) of the shift register (storage means 22) via a switch 33. . This switch 33 is turned on according to the detection output obtained from the defect detection circuit 31 via the delay circuit 34. In the case of the example shown in FIG. 1, the interpolation circuit 32 performs any average value interpolation that averages the data before and after the defective data, and the delay amount of the delay circuit 34 is one sector, or the amount of delay related to the tracking error described above. This is one word of data.

That is, for example, when the defect is detected in the servo signal of the first sector, the next time the tracking error related data of +1 sector is sent to the first stage of the shift register (storage means 22), the switch is activated. 33 is turned on, and the interpolated data obtained by interpolating the average value using each data of the 11th sector and +1 sector before and after the 1st sector is sent to the second stage of the shift register.

By the way, in this embodiment, the basic principle of the tracking control operation is to use the current tracking error data to control the head position after one rotation. To explain this in conjunction with Fig. 3, this Fig. 3 shows the index pulse IXP obtained for each rotation of the disk, and it shows how the index pulse IXP is obtained each time the disk rotates. It shows the track position. The track position in Figure 3 is the reference head trajectory (ideal trunk center) as the disc rotates.
It shows the radial position of the actual recording track relative to the position, and it is assumed that the n-th rotation of the disk coincides with the (n+1)-th rotation.

On the other hand, the amount of deviation between the magnetic head and the track,
A so-called tracking error is detected for each sector as the disk rotates. Now, let the track position in the i-th sector be trp(i), and the magnetic head position in the i-th sector (the head position relative to the ideal track center) in the n-th rotation of the disk be h.
When dp(+, n), the above tracking error in the i-th sector in the n-th round is trp(i)-h
It is expressed as dp(i,n). Based on the tracking error data in the first sector in the nth cycle, the next
+1 Same port, head position hdp(i, n
+1), for example, where a is a constant that satisfies 0<a<1. Note that the left side of this equation 0 indicates the control target position of the magnetic head in the (n+1)th port and the 1st sector, but if the characteristics of the tracking fine movement control B circuit 25 and the actuator are linear, it will not be the actual position. Since it can also be used as the head position, it is shown as hdp(i, n+1).

The magnetic head performs the above-mentioned control operation in the first rotation on the nth rotation.
Focusing on the point in time when sector No. 1 is being scanned, the tracking error data a(L
+ Lx) is the above a(trp(i)-hdp(i,
Corresponds to n)). Then, since the head position detection circuit 20 gives the current head position data hdp(i, n), the adder 21 gives the next (n+1)th control purpose head position data hdp(i+n÷1). to do
dp(i,n) +a(trp(+)−hdp(i,n
)) is obtained. Here, from the one-round delay circuit 22,
Added data in the next sector (i+1) one round before (n-1 same day), i.e. hdp(i+1.n-1)+a(trp(i+1)-h
dp(++1.n-1)) is the i+th next to the current nth same day
Control purpose head position data hdp(i+1
．． n).

Therefore, when starting to scan the next i+1 sector, the magnetic head only needs to be slightly controlled from the current head position hdρ(i,n) to the control target head position hdp(++1.n). The comparator 2 calculates hdp(++1.n)-hdp(i,n) corresponding to the head movement distance of
3 and sent to the tracking fine movement control circuit 25 via the phase control circuit 24. In addition, head movement amount data (including positive and negative directions) from the comparator 23 is sent to the head position detection circuit 20, and the current head position is determined by cumulatively adding (accumulating) the data in consideration of the positive and negative scratching characteristics. I'm looking for it.

By the way, in the embodiment of the present invention, the addition output from the adder 21 is stored in the storage means 2 as tracking error related data.
2, and the above-mentioned defective data interpolation processing is performed on this addition output data, but the tracking error data itself may be sent as is to the storage means and defective data interpolation is performed. The tracking error data obtained sequentially at each time is '1. ! z,
Let ys be data y! When a defect occurs in the servo signal corresponding to (yt+ys)/2, the data yt
Let us consider the reliability of interpolated data when interpolating.

The tracking error y is generally expressed as a function of the position (angular position, e.g. radians) in the disk rotation direction, but the main component of the error is the first-order mode that occurs at a rate of one period per rotation of the disk. There is a component A and a second-order mode component B that occurs at a rate of two periods per rotation, and these two components are approximately expressed as y = Asinx + Bs1n (2x + C). Here, the above first mode component A corresponds to the amount of center position deviation or eccentricity that occurs when the floppy disk is clamped or chaffed to a rotational drive shaft, etc., and the above second mode component B corresponds to the amount of center position deviation or eccentricity that occurs when the floppy disk is clamped or chaffed to a rotational drive shaft, etc. (elliptic deformation) amount, and C in the formula is the above first mode component and 2
This corresponds to the phase difference between the second mode component and the second mode component. Now, let the positions of each servo area of three sectors that appear sequentially as the disk rotates be X++Xz+Xz, and the tracking error data obtained from each of these servo signals is yl. Let it be yi+3's. Assuming that the sectors are arranged at equal intervals of ΔX along the tracking direction, xt=x, +Δx, x, =x, +2ΔX, so y+=Asinx+1Bs1n(2x++C)yz−A
sin(x++Δx) + B 5in(2(x++Δ
x)+C)ys=Asin(x++2Δx)+B 5
in(2(x++2Δx) 1C). 0' here
Comparing l+yri/2 and y2, (y++ys)/2 = y2(Asin x ++As1n (to x++2Δ)
+Bs1n(2x++C)+Bs1n(2(x++2Δ
x)+C))=! 4(2Asin(2(x+1Δx)
/2)-cos(-2Δx72)+28sin(2(2
(xt+ΔX)+C)/2)-Cog(-2Δx/2)
)=Asin(Xt+Δx)・cos(ΔX)+Bs1
n(2(x++Δx)+C)・cos(ΔX)=cos
(△X) X(Asin(x++Δx) + B 5in(2(x
++Δx) +C) )= cos (ΔX)・y! The above ΔX is a value determined by the number of sectors per l track N. For example, in the case of N-33, Δx=2π/3
3 (radians) cos (Δx) = cos (2π/33)! :i 0.
9B, the error between (y++ys)/2 and y2 is only about 2%, and the interpolated data can be used as a sufficient substitute for the true data.

As a result, even if a defect occurs in the servo signal, the tracking error data at the defective position can be interpolated from the tracking error data based on the servo signals of the sectors before and after the defect, and highly accurate tracking control can be achieved.

It should be noted that the present invention is not limited to the above-described embodiment, and for example, as the storage means 22, a normal RAM (Random Access Memory) or the like may be used in addition to a shift register. In addition, the present invention can be applied not only to tracking control based on tracking error data from one lap before, but also to normal tracking control. In this case, current data is predictively interpolated from multiple past data. In addition, instead of average value interpolation, previous value hold or higher-order interpolation of third or higher order may be performed.In addition, for example, in addition to flexible magnetic disks, hard magnetic The present invention may be applied to a disk or an optical or magneto-optical disk-shaped recording medium, and various modifications can be made without departing from the gist of the present invention.

H0 Effects of the Invention When normal tracking error related data cannot be obtained due to a defect in the servo signal, tracking error related data corresponding to the defective servo signal can be obtained based on other normal tracking error related data from the storage means. Because it is determined through interpolation, highly accurate tracking can be achieved.

Further, according to the embodiment of the present invention, although the track position on the disk changes during one rotation of the disk, its appearance is approximately the same between the n-th rotation and the n+1-th opening. Focusing on this, tracking control is performed using tracking error-related data delayed by one round, that is, fine movement control of the head position on the n-th round is performed using data from the n-1th same position. Highly accurate tracking control can be achieved with an extremely simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing a schematic configuration of a tracking control device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the detection operation of a servo signal recorded on a disk, and FIG. FIG. 4 is a waveform diagram for explaining the basic principle of tracking control operation, and a schematic plan view showing an example of a disc recording format. ■・・・・・・・・・Magnetic disk S・・・・・・・・・Servo area D・・・・・・・・・Data area 11・・・Magnetic head l3... Envelope detection circuit 14...
... Servo 10 detection circuit 1B ... Subtractor 19 ... Multiplier 20 ... Head position detection circuit 21 ...
... Adder 22 ... Storage means 23 ... Comparator 25 ... Tracking fine movement control circuit 31
......Defect detection circuit 32...Interpolation circuit 33...Switch

Claims (1)

[Scope of Claims] A playback head that plays back at least a plurality of servo signals recorded discretely along the rotational direction of a disk, and the presence or absence of defects in the servo signals read from the disk by the playback head. a tracking error detection unit that detects a tracking error as a positional deviation of the reproducing head with respect to the recording track position on the disk based on the servo signal; a storage means for storing related data; an interpolation means for interpolating tracking error-related data corresponding to the servo signal in which the defect is detected based on the tracking error-related data read from the storage means; A tracking control device comprising means for controlling tracking of the head in accordance with tracking error related data obtained from the interpolation means.