JPH03189972A - Track follow-up controller - Google Patents

Abstract

PURPOSE:To obtain sufficient track follow-up performance even if a sector number is small by providing a track waviness estimating means and a second positional errornous signal generating means to generate a second positional errornous signal showing the positional shearing quantity between a head and a targeted track and positional-controling the head with use of the second positional errornous signal. CONSTITUTION:A track waviness signal 23 among samples obtained by a track waviness estimating means 17 is added and a second positional errornous signal 20 is obtained. Since a head positional signal 21 is a continuous signal and also the track waviness signal 23 can be obtained apploximately continuously, also the positional errornous signal can be obtained approximately continuously. Then, compensating operation is executed approximately continuously in a control means 13 with use of the second positional errornous signal and by making the operation result as the command of an actuator 14 and displacing a head 11 to follow up a track. Thus, even if a sector number is small and a servo signal number is small, sufficient tracking follow-up performance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention (Part 1) relates to a track following control device in a disk device.Related Art In a flexible magnetic disk device, track density is increased in order to increase recording capacity. However, head positioning in conventional flexible magnetic disk devices is generally performed using an open-loop method using a stepping motor. Track runout (eccentricity) occurs due to chucking misalignment and temperature/humidity expansion of the medium.With conventional positioning methods, when the amount of track runout becomes a non-negligible amount relative to the track pitch, the magnetic head can accurately track the data. Since data is recorded and reproduced across adjacent tracks without being positioned above the disk surface, the reliability of data decreases. Track following control is required to position the magnetic head on a predetermined track by detecting a position error signal from the servo signal reproduced by the magnetic head.

Track following control called the sector servo method is implemented in hard disk drives. In this method, the data surface is divided into multiple sectors, a servo signal is recorded in a portion of each sector, and this signal is reproduced by a magnetic head. A track position error signal is generated, and based on this signal, the voltage or current of the head drive actuator is controlled to position the head on the data track. Research is underway to apply this sector servo system to flexible disk drives to achieve high track density. A conventional sector servo system in a flexible disk device will be described below.

FIG. 4 shows a recording medium on which servo signals are recorded. In the figure, the recording area on one or both sides of the recording medium is divided into sectors 41, and each sector is further divided into data areas 43.
and a servo area 42. An outline of each sector is shown in FIG. 5. In the figure, in the servo area 42, servo signals are recorded alternately at positions shifted by half a track with respect to the track 44. Also, the recording medium is moving in the track direction. As shown in the figure, the head 11 moves in the radial direction of the recording medium and is controlled to be positioned at the center of the track. 11. The position error signal generating means 32 detects the servo signal reproduced for each sector and outputs the signal to the head 11.
The control means 33 performs a compensation calculation based on the position error signal 36 and outputs a command signal to the actuator 14. The actuator 14ζ moves the head 11 according to the command signal and positions it on the track.

(For example, Nikkei Electronics 1987.1.26
No, 413) Problems to be Solved by the Invention However, in the sector servo system as described above, the track following performance improves as the number of main signals, that is, the number of sectors increases. The occupied area is reduced and the storage capacity is reduced. Moving on to the next step, flexible disk devices have a larger amount of track deflection than hard disk devices, so in order to obtain sufficient track following performance, a large number of sectors are required, resulting in a reduction in storage capacity. For example, if the number of sectors is 40,
If the disk rotation speed is 60 Orpm, the sampling frequency of the position error signal obtained from each sector is 400H.
Generally speaking, considering the stability of the EL control system in a sampling value control system, the servo band can be limited to about 1/7 of the sampling frequency.
The frequency is about 7Hz, which is the fundamental frequency of track vibration.
Hz, the gain of the servo system is only about 10 dB, and there is a problem that sufficient track following performance cannot be obtained.9 The present invention solves these problems, and even if the number of sectors is small, It is an object of the present invention to provide a track following control device that can obtain sufficient track following performance. A recording medium in which a servo signal is recorded sector by sector, a head that reproduces the servo signal recorded on the recording medium, and a first head that detects the servo signal of each sector in a sample manner and indicates the amount of positional deviation between the target track and the head. A first position error signal generation means for generating a position error signal; a position detection means for detecting the absolute position of the head; and a first position error signal generation means for detecting the absolute position of the head; track waviness estimating means for estimating track waviness information between samples based on the track wobbling data; a second position error signal generating means for generating a second position error signal indicating a positional deviation scene with respect to the target track;
The position of the head is controlled using the position error signal of the head.

According to the present invention, track waviness information between samples is obtained from track waviness data obtained from an arbitrary track by the track waviness estimating means.

The head position can be continuously determined by the position detection means, and it is also possible to determine how the position error signal changes between samples.

Therefore, it is possible to obtain more position error signals than the number of sectors from the position error signal sampled for each sector from the servo signal stored on the recording medium and the amount of change in the position error signal between samples. The sampling frequency of the sample value control system can be improved,
It is possible to expand the servo band more than the conventional sector servo method, and it is possible to obtain sufficient track following performance even when there is a large track shake.4 Furthermore, according to this method, it is possible to obtain sufficient track following performance. It is also possible to reduce the number of storage sectors and expand the storage capacity.Example 1 Hereinafter, a track following control device according to an embodiment of the present invention will be explained with reference to the drawings. This figure shows the configuration of the track following control device of the invention. 4 In FIG. 1, 11 is a head.

12 is a first position error signal generation means 13 is a control means
14 is an actuator, 15 is a recording medium 16 is a second position error signal generation means, 17 is a track waviness estimation means, 18 is a position detection hand Q, and 19 is a first position error signal.
Reference numeral 20 indicates a second position error signal, and reference numeral 21 indicates a head position signal. A recording medium 15 on which servo signals are recorded sector by sector is rotating, and when the servo area passes the head 11, the data signal and the servo signal are reproduced and sent to the first position error signal generating means 12. The first position error signal generating means 12ζ detects the servo signal and generates the first position error signal 19 up to the target track as a sample. 18 is a position detecting means, which constantly detects the absolute position of the head. 17 is a track waviness estimating means which detects and outputs a head position signal 21, and outputs a first position error signal 1.
9 and a head position signal 21 detected by the position detection means 18
The method estimates the amount of track waviness between samples and outputs a track waviness signal 23 to the second position error signal generating means.Next, based on FIG. 2, a method for estimating the amount of track waviness between samples Explain. Figure 2 41)
Explaining rack runout and track waviness. Otori (a) shows the actual track runout. L (b) shows the track runout information sampled for each sector. LA (c) shows the sector estimated by the track waviness estimator. It shows the track undulations in between. To the previous number in which track following control is started, first, the control means 13 performs a compensation calculation using the head position signal 21, controls the actuator 14, and controls the head position signal 21.
At this time, since the head 11 is stationary, the first position error signal →-10-19 indicates track runout information and is sampled as shown in FIG. 2(b). Ru. Amount of track waviness between sectors (double) This is the amount of change in track wobbling from one sample point to the next as shown in Figure 2 (C), and is obtained sample-wise as shown in Figure 2 (b). It can be estimated by performing arithmetic operations (for example, Lagrange's interpolation method) using the track runout information obtained.When the above processing is completed, track following control is started, but the operation during track following control is described below. To explain, when the servo area 42 shown in FIG. 4 recorded on the recording medium 15 passes the head, the first position error signal 19 is sampled by the first position error signal generating means 12 and at the same time The signal 22 is transmitted to the track waviness estimating means 17 and the second
output to the position error signal generating means 16. The track waviness estimating means 17 outputs track waviness information obtained from an arbitrary track to the second position error signal generating means 16 in phase with the track wobbling of the recording medium 15 according to the timing signal 22 . When the timing signal 22 is input, the second position error signal generating means 16 stores the head position signal 21 at that time. Further, the difference between this stored head position signal and the continuous head position signal 21 is calculated to calculate the amount of displacement of the head from the position where the servo signal was sampled, and this calculation result is combined with the first position error signal 1.
Track swell estimation means 17
The inter-sample track waviness signal 23 obtained by
are added to obtain the second position error signal 20. The head position signal 21 is a continuous signal, and the track waviness signal 23
The position error signal 20, which can be obtained substantially continuously, can also be obtained substantially continuously. Therefore, in the conventional example, ζ
The position error signal, which was previously obtained only in sectors, can now be obtained almost continuously. This second position error signal 20
The control means 13 performs a compensation calculation almost continuously using the following (\This calculation result is used as a command for the actuator 14 to displace the head 11 to follow the track, thereby obtaining sufficient track following performance. Become.

1-12- In order to obtain the track waviness signal 23 in the embodiment, the track wobbling was determined by fixing the position of the head 11. Using the first position error signal 19, the control means 13
Track following control is performed by the actuator 14 (＼
At this time, the head position signal 21 and the first position error signal I
Track runout can be determined from 9. In addition, in the embodiment, the second position error signal No. 20 has a substantially continuous force (calculated at least once between samples, so that the sampling frequency is at least twice that of the first position error signal 19). 4Q The second position error signal 20 is caused by an external shock, etc. to the head 1.
1 is displaced, the amount of positional deviation between the bed 11 and the track can be immediately known.It can be used as a track deviation detector, and data writing is immediately prohibited based on the second position error signal 20. In addition, as an example, the present invention can be applied to hard disks, optical disks, etc. Effects of the Invention As described above, the present invention includes a recording medium in which a servo signal is recorded in each sector, a head for reproducing the servo signal recorded on the recording medium, and a sample of the servo signal in each sector to detect the target track. a first position error signal generating means for generating a first position error signal indicating the amount of positional deviation of the head; a position detecting means for detecting the absolute position of the head; and a servo signal of an arbitrary track read in advance by the head. Track waviness estimating means for obtaining track waviness data in each sector as samples, and estimating track waviness information between samples from these track wobble data; By providing a second position error signal generation means for generating a second position error signal indicating the amount of positional deviation between the head and the target track based on the waviness information, a position error signal indicating the amount of positional deviation between the track and the head is provided. Since the apparent bling frequency can be made higher, the gain of the servo system can be ensured sufficiently against track runout, and the track density can be increased, resulting in higher capacity.Also, the number of sectors is small, making it possible to increase the servo system's gain. With a small number of signals, sufficient tracking performance can be obtained, and the area occupied by the servo signals on the recording medium can be reduced, allowing for higher capacity.

[Brief explanation of drawings]

FIG. 1 shows the configuration of a track following control device in an embodiment of the present invention. FIG. 2 is an explanatory diagram of track runout and track waviness. FIG. 3 shows the configuration of a conventional track following control device. FIG. 4 shows the configuration of a recording medium. Explanatory Diagram FIG. 5 is an explanatory diagram of sectors.

Claims (4)

[Claims] (1) A recording medium on which a servo signal is recorded sector by sector, a head that reproduces the servo signal recorded on the recording medium, and a sample that detects the servo signal of each sector and positions the target track and the head. first position error signal generation means for generating a first position error signal indicating the amount of deviation;
position detecting means for detecting the absolute position of the head, and obtaining sample track runout data in each sector from a servo signal of an arbitrary track read in advance by the head, and detecting between samples based on these track runout data. track waviness estimating means for estimating track waviness information of the head; and a second track waviness estimating means for estimating the amount of positional deviation between the head and the target track based on the first position error signal, the absolute position of the head, and the track waviness information. a second position error signal generation means for generating a position error signal, and the track following control device is characterized in that the second position error signal is used to control the position of the head with respect to the target track. . (2) The track runout data obtained as a sample from the servo signal of an arbitrary track is configured such that the head position is fixed and is determined from the first position error signal obtained at that time. Track following control device according to scope 1. (3) The track runout data obtained from the servo signal of an arbitrary track is obtained by adding the head position subjected to tracking control and the first position error signal. Track following control device as described in . (4) The second position error signal is generated by subtracting the amount of head movement from the head position when the servo signal was detected from the first position error signal, and calculating the track waviness information between sectors. The track following control device according to claim 1, characterized in that the track following control device generates by adding.