JP2553721B2 - Track following control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track following control device in a disk device.

2. Description of the Related Art In recent years, studies have been conducted on a method of increasing the track density in order to increase the recording capacity of a flexible magnetic disk device. Head positioning in a conventional flexible magnetic disk device is generally performed by an open loop method using a stepping motor. In the flexible magnetic disk device, track deflection (eccentricity) occurs due to chucking displacement and expansion of the temperature and humidity of the medium that occur when the medium is mounted in the device. In the conventional positioning method, when the amount of track deviation becomes a non-negligible amount with respect to the track pitch, the magnetic head is not accurately positioned on the data track and recording / reproduction is performed across adjacent tracks. Is reduced. Therefore, in order to achieve high track density in the flexible magnetic disk device,
It is necessary to record the servo signal on the disk surface and detect the position error signal from the servo signal reproduced by the magnetic head to position the magnetic head on a predetermined track.

In a hard disk drive, track follow-up control called the sector servo system is implemented. This system divides the data surface into multiple sectors, records a servo signal in part of each sector, and reproduces this signal with a magnetic head. Then, a track position error signal is generated, and the voltage or current of the head drive actuator is controlled based on this signal to perform positioning on the data track. Studies have been conducted to realize a high track density by applying this sector servo system to a flexible magnetic disk device. The conventional sector servo system in the flexible disk device will be described below.

FIG. 4 shows a recording medium on which servo signals are recorded. In the drawing, the recording area on one side or both sides of the recording medium is divided into sectors 41, and each sector is further divided into a data area 43 and a servo area 42. ing. FIG. 5 shows an outline of each sector. In the figure, the servo area 42 has a track 44
Servo signals are recorded alternately at a position shifted by a half track with respect to. The recording medium is moving in the track direction. The head 11 moves in the radial direction of the recording medium as shown in the figure, and is positioned and controlled at the track center. FIG. 3 shows a conventional track following control device. The servo signal recorded in each sector is reproduced by the head 11. The position error signal generating means 32 detects the servo signal reproduced for each sector and generates a position error signal 36 indicating the deviation between the head 11 and the track 44. The control means 33 performs compensation calculation based on the position error signal 36 and outputs a command signal to the actuator 14. The actuator 14 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 tracking performance is improved as the number of servo signals, that is, the number of sectors is increased. Since the amount of data increases, the area occupied by data decreases and the storage capacity decreases. Further, since the flexible disk device has a large amount of track deviation as compared with the hard disk device, many sectors are required to obtain sufficient track following performance and the storage capacity is reduced. For example, if the number of sectors is 40 and the disk rotation speed is 600 rpm, the sampling frequency of the position error signal obtained from each sector is 400 Hz. Generally, in a sampling value control system, considering the stability of the control system, the servo band is limited to about 1/7 of the sampling frequency. Therefore, the servo band is about 57 Hz, and the gain of the servo system at 10 Hz, which is the basic frequency of track shake, is 10 dB.
However, there is a problem that sufficient track following performance cannot be obtained.

The present invention is to solve such problems,
It is an object of the present invention to provide a track following control device that can obtain sufficient track following performance even if the number of sectors is small.

Means for Solving the Problems In order to solve the above problems, the track following control method of the present invention is a recording medium in which a servo signal is recorded for each sector, and a head for reproducing the servo signal recorded in the recording medium, First position error signal generating means for detecting the servo signal of each sector in a sample manner and generating a first position error signal indicating the amount of positional deviation between the target track and the head, and position detecting means for detecting the absolute position of the head. A track waviness estimation means for estimating track waviness data in each sector from the servo signal of an arbitrary track read in advance by the head, and estimating track waviness information between samples based on these track wobble data. , The first position error signal, the absolute position of the head, and track waviness information based on the head and the target track. A second position error signal generating means for generating a second position error signal indicating the amount of positional deviation from the clock.
The position of the head is controlled by using the position error signal of.

Effect According to the present invention, track waviness estimation means obtains track waviness information between samples from track wobbling data obtained from an arbitrary track. Since the head position can be continuously known by the position detecting means, it is possible to know 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 in the recording medium and the change amount of the position error signal between samples. Therefore, apparently, the sampling frequency of the sample value control system can be improved, the servo band can be expanded more than the conventional sector servo system, and sufficient track following performance can be obtained even when there is a large track deviation. Is possible. Furthermore, according to this method, since sufficient track following performance can be obtained, it is also possible to reduce the number of sectors and expand the storage capacity.

Embodiment A track following control device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of the track following control device of the present invention. In FIG. 1, 11 is a head, 12 is a first position error signal generating means, 13 is a control means, 14 is an actuator, 15 is a recording medium, 16 is a second position error signal generating means, 1
Reference numeral 7 is a track waviness estimating means, 18 is a position detecting means, 19 is a first position error signal, 20 is a second position error signal, and 21 is a head position signal. The operation will be described below with reference to FIGS. 1 and 2.

In FIG. 1, the storage medium 15 in which the servo signal is recorded for each 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 12 detects the servo signal and generates the first position error signal 19 up to the target track on a sample basis. Reference numeral 18 denotes a position detecting means, which constantly detects the absolute position of the head and outputs a head position signal 21. Reference numeral 17 is a track waviness estimation means, which estimates the track waviness amount between samples from the first position error signal 19 and the head position signal 21 detected by the position detection means 18 and tracks to the second position error signal generation means. The swell signal 23 is output. Next, the method of estimating the track waviness amount between samples will be described with reference to FIG. FIG. 2 is a diagram for explaining track wobbling and track waviness, where (a) shows actual track wobbling,
(B) shows the track deviation information sampled for each sector, and (c) shows the track waviness between sectors estimated by the track waviness estimator. First, before activating the track following control, first, the head position signal 21 is used to perform compensation calculation by the control means 13 to control the actuator 14 to fix the position of the head 11. At this time, since the head 11 is stationary, the first position error signal 19 indicates track deviation information and is sampled as shown in FIG. 2 (b). The amount of track waviness between sectors is the amount of change in track deviation from the sample point to the next sample as shown in FIG. 2 (c), and is obtained for the sample shown in FIG. 2 (b). It can be estimated by performing an arithmetic operation (for example, Lagrange's interpolation method) using the track shake information. When the above process is completed, the track follow-up control is started. The operation during the track follow-up control will be described below. When the servo area 42 shown in FIG. 4 stored in the storage medium 15 passes through the head, the first position error signal generating means 12 samples the first position error signal 19 and simultaneously outputs the timing signal 22. It is output to the track waviness estimation means 17 and the second position error signal generation means 16. The track waviness estimation means 17 outputs the track waviness information obtained from an arbitrary track in phase with the track wobble of the recording medium 15 by the timing signal 22 to the second position error signal generation means 16. When the timing signal 22 is input, the second position error signal generation means 16 stores the head position signal 21 at that time. Further, the difference between the stored head position signal and the continuous head position signal 21 is calculated to calculate the displacement amount of the head from the position where the servo signal is sampled, and the first position error signal is sampled. The first position error signal indicating the deviation between the head and the target track at the time, and the difference between the calculation result of the displacement amount of the head from the sample position described above are taken, and further from the sample position obtained by the track waviness estimation means 17. The track waviness signal 23 shown in FIG. 2 (c), which is the track runout, is added to obtain the second position error signal 20. Since the head position signal 21 is a continuous signal and the track waviness signal 23 can be obtained substantially continuously, the position error signal 20 can also be obtained substantially continuously. Therefore, in the conventional example, the position error signal, which was obtained only with the number of sectors, is obtained substantially continuously.
Compensation calculation is performed substantially continuously in the control means 13 using the second position error signal 20, and the result of this calculation is used as a command for the actuator 14 to displace the head 11 so as to follow the track, thereby achieving sufficient track following. Performance will be obtained.

In the embodiment, in order to obtain the track waviness signal 23 shown in FIG. 2 (c), the position of the head 11 was fixed and the track runout shown in FIG. 2 (b) was obtained, but as shown in FIG. With the same configuration as the conventional one, track tracking control is performed by the first position error signal 19 (position error signal 36 in FIG. 3),
The head position signal 21 at this time and the first position error signal 19 are added to obtain the track deviation shown in FIG. 2B for the following reason. This is because if the head position signal 21 is X and the track shake is Y, the first position error signal 19 indicates the amount of positional deviation between the track and the head.
It means that X is detected. Therefore, if the first position error signal 19 (Y-X) and the head position signal 21X are added at the sample position of the servo signal, the signal of FIG. 2 (b) is obtained. In the embodiment, the second position error signal 20 is assumed to be substantially continuous. However, if the second position error signal 20 is calculated at least once between samples, the sampling frequency is at least twice that of the first position error signal 19. Therefore, the track following performance superior to the conventional one can be obtained. Further, the second position error signal 20 can be used as a track deviation detector because the positional deviation amount between the head 11 and the track can be immediately known even when the head 11 is displaced due to an external impact or the like. Therefore, based on the second position error signal 20, it is possible to promptly prohibit the data writing and improve the reliability of the data. Although the flexible disk device has been described as an embodiment, it goes without saying that the present invention can be applied to a hard disk, an optical disk and the like.

As described above, according to the present invention, the recording medium in which the servo signal is recorded for each sector, the head for reproducing the servo signal stored in the recording medium, the servo signal of each sector is detected in a sample, and the target track is detected. And a first position error signal generating means for generating a first position error signal indicating the position displacement amount 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 data for each sector is obtained as a sample, and track waviness estimation means for estimating track waviness information between samples from these track wobbling data, a first position error signal, the absolute position of the head, and a track waviness A second position for generating a second position error signal indicating the amount of positional deviation between the head and the target track from the information. By providing the error signal generating means, the sampling frequency of the position error signal indicating the positional deviation amount between the track and the head can be apparently increased, so that the gain of the servo system can be sufficiently secured against the track shake and the track density can be increased. Therefore, the capacity can be increased. Also,
Even if the number of sectors is small and the number of servo signals is small, sufficient tracking follow-up performance can be obtained, so that the area occupied by the servo signals of the recording medium can be reduced and the capacity can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram of a track follow-up control device in one embodiment of the present invention, FIG. 2 is an explanatory diagram of track runout and track waviness, FIG. 3 is a block diagram of a conventional track follow-up control device, and FIG. FIG. 5 is an explanatory diagram of a recording medium, and FIG. 5 is an explanatory diagram of sectors. 11 ... Head, 12 ... First position error signal generating means, 13
...... Control means, 14 ...... Actuator, 15 ...... Storage medium, 16 ...... Second position error signal generation means, 17 ...... Track waviness estimation means, 18 ...... Position detection means

Claims (4)

(57) [Claims] 1. A recording medium on which a servo signal is recorded for each sector, a head for reproducing the servo signal recorded on the recording medium, a target track and the head for detecting the servo signal of each sector in a sample manner. The first position error signal generating means for generating a first position error signal indicating the amount of positional deviation of the head, the position detecting means for detecting the absolute position of the head, and the servo signal of an arbitrary track read in advance by the head. Track waviness estimation means for obtaining track wobbling data in each sector on a sample basis and estimating track waviness information between samples based on these track wobbling data, the first position error signal and the absolute position of the head. And a second position indicating the amount of positional deviation between the head and the target track based on the track waviness information. And a second position error signal generating means for generating a difference signal, track following control apparatus characterized by controlling the position the head relative to the target track by using the second position error signal. 2. A track deviation data sampled from a servo signal of an arbitrary track has a structure in which the head position is fixed and the data is obtained from a first position error signal obtained at that time. Claim 1st
A track following control device according to the item. 3. Track deviation data obtained from a servo signal of an arbitrary track is
The track following control device according to claim 1, wherein the head position signal subjected to tracking control and the first position error signal are added to obtain the value. 4. The second position error signal is obtained by subtracting the head movement amount from the first position error signal from the head position when the servo signal is detected as a starting point, to thereby obtain track waviness between sectors. The track-following control device according to claim 1, wherein the information is generated by adding information.