JPH03119579A - Head positioning device for magnetic disk and magnetic disk medium - Google Patents

Abstract

PURPOSE:To position a head with a high precision regardless of track deflection by detecting the deviation between the actual position of a track and an estimated position on the way of sampling of servo information and giving it as a position error signal to a positioning means. CONSTITUTION:When a magnetic head 3 is on a data zone 7, the magnetic head 3 reproduces servo information in each servo sector 8D, and a muCPU 20 obtains a position error signal E1(S) and outputs it to a compensator 24 through a D/A converter 23 and a notch filter 26. The output is used as a control signal. In this case, the muCPU 20 takes in the present position of moving mechanism 4 obtained from an optical sensor 5 between the servo sector 8D and the next servo sector 8D, namely, a middle period T2 between sampling periods T1 and T3 and obtains an estimated error signal E2(S) in accordance with the difference of the estimated track position and performs the control to approximate the movement locus to the actual track position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a sector servo type magnetic disk head positioning device.

(Prior art) In general, in a sector servo type magnetic disk, a servo sector is provided for each sector obtained by dividing the magnetic disk medium radially at equal intervals, and servo information for head positioning is stored in this servo sector. To read information with a magnetic head and follow a predetermined track.

However, magnetic disk media are subject to anisotropic expansion and contraction effects due to the influence of temperature and humidity, although the degree varies depending on the material, and the perfect circle of each track is more or less deformed into an irregular circle. Further, especially in magnetic disk media such as floppy disks in which the medium is exchanged with respect to a spindle, the center of the Druck circle shifts from the center of the spindle due to chucking errors.

Conventionally, in order to avoid the effects of track shake as much as possible and obtain good servo followability, the number of servo sectors has been increased as much as possible, and the sampling period of servo information determined by the number of each servo sector has been shortened.

(Problem to be solved by the invention) However, the number of servo sectors is generally determined in consideration of the amount of data to be recorded and reproduced, and especially in floppy disk devices, it is necessary to keep the number of servo sectors to about 38 in order to improve format efficiency. There is a problem that the number of sectors cannot be increased arbitrarily.

Another problem is that when only information from the servo sector is used, a position error signal cannot be obtained from one sector to the next, resulting in poor response when the head goes off-track due to external disturbances, etc. There is a point.

Furthermore, in sample value control systems, there is generally a phase delay due to sample and hold, and in order to prevent this phase delay from affecting the control system, it is necessary to limit the servo band to about 1/7 or less of the sampling frequency. Therefore, the gain decreases in the frequency band of track runout, resulting in a problem that sufficient track followability cannot be achieved.

Therefore, the present invention has been made in consideration of these circumstances, and includes: - A magnetic disk head that allows highly accurate head positioning even when track wobbling occurs without increasing the servo information on the disk medium. The object of the present invention is to provide a positioning device and a magnetic disk medium used therein.

[Structure of the invention]

(Means for Solving the Problems) The present invention, which solves the second problem, as shown in FIG. In a magnetic disk head positioning device that guides the magnetic head along a predetermined track while reading servo information provided in each sector with a magnetic head, the deviation of the track with respect to the center of the rotation axis is stored in advance as track runout information. track runout information storage means C1; positioning means C2 for forming a position error signal for the magnetic head based on servo information read in each sector and positioning the magnetic head on a predetermined trunk; and a current position of the magnetic head. current position detecting means C3 for detecting the current position; and track position estimating means C4 for estimating the actual position of the track while the magnetic head is reading the servo information of the next sector from the track runout information in the storage means C]; an estimated error signal forming means C5 for forming an estimated error signal from the difference between the track position estimated by the means C4 and the current position detected by the current position detecting means C3; The present invention is characterized in that it includes an intermediate signal providing means C6 which is provided as a position error signal of the positioning means in the middle of the sector.

Further, the magnetic disk medium of the present invention used in the head positioning device is characterized in that the number of sectors in the guard zone is greater than that in the data zone in a servo sector type magnetic disk medium having a guard zone and a data zone.

(Function) In the magnetic disk positioning device of the present invention, during the sampling of servo information of each servo sector, the track position estimating means C4 and the estimated error signal forming means C5 detect the deviation between the actual position and the estimated track position. This is detected and used as a position error signal for the positioning means C2.

Therefore, in the head positioning device of the present invention, by inserting an appropriate number of estimated error signals between servo sectors, the position error signal is equivalently increased, and track following performance and disturbance characteristics can be improved. can.

Furthermore, in the magnetic disk medium of the present invention, since a larger number of servo sectors are provided in the guard zone than in the data zone, track followability in the cart zone can be improved and accurate track runout information can be collected there.

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

FIG. 2 is an explanatory diagram of a magnetic disk positioning device according to an embodiment of the present invention.

As shown in the figure, the positioning device of this example has a positioning mechanism for a magnetic disk medium 2 which is rotationally driven by the rotation of a spindle 1.
A magnetic head 3 for recording and reproducing information is provided, and the magnetic head 3 is configured to be movable in the radial direction of the disk medium 2 by a moving mechanism 4.

The moving mechanism 4 is, for example, a linear voice coil motor (LV
CM), which positions the magnetic head 3 at a predetermined radial position relative to the magnetic disk medium 2 in accordance with a control signal.

The moving mechanism 4 is provided with an optical sensor 5 for detecting displacement with respect to a base to which the spindle is fixed. This sensor 5 is adapted to read a scale LS provided on the side surface of the moving mechanism 4, and can detect the current position of the moving mechanism 4 and the Zunawa magnetic head.

As shown in FIG. 3, on one or both sides of the magnetic disk medium, a guard zone 6 is provided on the outer periphery and a data zone 7 is provided on the inner periphery, similar to well-known devices. are provided with sabot sectors 8G and 8D, respectively. It is assumed that the number of sectors 8D in the data zone 7 in this example is about 38, similar to the conventional one. It is also assumed that the number of servo sectors 8G in the guard zone 6 is twice the number of sectors in the data zone 7 (76). 9 indicates the pig sector. 10 indicates the sector interval of the data zone.

In addition, as shown in FIG. 4, the servo sectors 8G and 8D
0, the erase section (ERASE') 11 and the AG
A zone detection section (ZONE) 13 for distinguishing between the C section 12, the guard zone 6, and the data zone 7, and the position section (PO3I S I 0) in which the servo pattern is written.
N) 14 are provided.

Therefore, the servo sector 8 by the magnetic head 3 of this example
In the detection of D and 8G, when the gap 15 shown in the center bone of FIG. can be matched.

Specifically, the magnetic head 3 reproduces signals from the left side to the right side as shown in FIG. 5, and the position section 14 reproduces four signals A, B, and C.

D is held at its peak, and a position error signal for the head positioning system is generated from A-B and CD, so that the gap 15 passes through the center of the track.

Referring again to FIG. 2, the positioning device of this example inputs the signal reproduced from the magnetic head 3 via the preamplifier 16, and inputs the signal to the AGC amplifier 17 and the peak hold circuit 18.
, a microcomputer (μ
(CPU) 20. The head positioning signal reproduced from the magnetic head 3 is sent to the servo sector 8D.

It will be sampled every 8G.

On the other hand, the position signal from the optical sensor 5 is a continuous signal,
The above A/
The signal is input to the D converter 19, A/D converted at an arbitrary period, and taken into the μCPU 20 for processing. Here, this data acquisition timing is determined by the servo sector at the sampling timing T, T3, which is exactly in the middle of T3.
Suppose that it is 2.

The device determining signal constituted by the μCPU 2'O is sent to the D/A converter 23, notch filter 26, and compensator 24.
The signal is output to the driver 25 via the driver 25, and the driver 25 drives the moving mechanism 4. The function of the notch filter 26 will be described later.

FIG. 6 is a block diagram showing a control model of the head positioning device of FIG. 2.

In the figure, Y (S) is the output, R1 (S) is the target value of the servo information system obtained by each 12 servo sectors 8D and 8G, R2 (S) is the target value of the sensor system input at the intermediate point, 27', 28 are comparators, El(S), E2 (
S) indicates an error signal. The μCPU 20 stores track runout information in an internal RAM 20M.

As a method for storing track runout information in the RAM 20M, the following two methods (1) and (2) can be used.

■ The magnetic head 3 is made to follow a specific track in the guard zone 6 using the error signal El (S) of the servo information system, and at this time, the error signal E'2 (of the current position system of the moving mechanism 4 obtained from the optical sensor 5) is S) into the μCPU 20, and the seventh
The track shape 29 shown in the figure is taken as track runout information.

In this example, as shown in FIG. 3, the number of servo sectors, 8G, is double the normal number (76), so the tracking performance is good and the track shape can be accurately captured.

(2) The magnetic head '3 is fixed on the guard zone 6, and the μCPU 20 reads the position error signal El(S) of the sabot information system for a specific track under the head 3, and the track shape 29 is captured. Also in this case, since the number of servo sectors is large, the track shape can be accurately captured.

The track shape 29 obtained as in (2) and (2) above is used as track deflection information indicating the degree of distortion of all tracks, and using this shape 29, for each track, following sampling of each servo information, It is possible to arbitrarily estimate the track position for the next control period with respect to the actual position of . The estimation method can be determined by interpolation calculation for each position of each track, but in order to perform high-speed processing, table data may be prepared for each position of each track.

Track runout information is collected, for example, after chucking the floppy disk. Furthermore, it may be performed in response to changes in temperature and humidity, or periodically. Furthermore, it is only necessary to perform this during a so-called free time, such as when data recording and reproduction are completed.

Now, after the above preparation procedures, the control device of this example has the following steps:
When the magnetic head 3 is in the data zone 7, the magnetic head 3 reproduces servo information for each servo sector 8D, and
U20 obtains a position error signal E1(S) and outputs it to the compensator 24 via the D/A converter 23. The output of this compensator 24 becomes a control signal.

At this time, at an intermediate time T2 between the servo sector 8D and the next servo sector 8D, that is, between the sampling times T and T3, the μCPU 20 takes in the current position of the moving mechanism 4 obtained from the optical sensor 5, and calculates the estimated l.rack. An estimated position error signal E2 (S) is obtained from the difference with the position.

In FIG. 8, Pl is the current position at time T1, 30 is the head traveling direction, 31 is the head movement trajectory, 32 is the actual track position, 33 is the estimated trunk position, and P2 is the time T1.
The actual track position at I and P3 indicate the current position at intermediate time T2. Note that the estimation error signal E2 (S
) is determined between the current position P3 and the l/rack estimated position 33, but as shown in the figure, the next control timing T3
It is not necessarily determined as the difference from the estimated value of , but can be determined as an arbitrary amount in relation to the control cycle.

To explain FIG. 8 in detail, the position error signal El (S) is generated by servo information with respect to the current position P1 at time T1.
is generated, and the magnetic head 3 is controlled to move in the direction of the actual track position P2 at this point as shown by the movement trajectory 3].

However, in this example, at the intermediate point T2 of the time point T3 at which the next servo information is obtained, a further error signal E2 (S) is obtained for the estimated I/rack position 33, and the movement trajectory 31 is moved to the actual track position 32. controlled to get closer. The compensator 24 receives position error signals E], (S) obtained from the magnetic head 3.
and the estimated error signal E2 (S) obtained from the optical sensor 5 are inputted alternately.

Here, if there is a difference in the position voltage conversion coefficient or the like between the magnetic head 3 and the optical sensor 5, an error occurs in the estimated error signal E2(S), which adversely affects the positioning accuracy. For example, when the estimated error signal E2(S) with an error is inserted at one midpoint between the Zumbrink cycles, the positioning error causes an oscillation phenomenon in the sampling cycle. Therefore, in this example, a notch filter 26 is inserted at the same frequency as the sampling frequency. Generally, notch filter 2
6, if the number of inserted estimation error signals E2 (S) is N, it is sufficient to suppress frequency components that are (N+1)/2 times.

This allows accurate track positioning even if the estimated error signal E2 (S) includes an error. In addition, since there is a possibility that the estimated value contains a relatively large error, in order to eliminate this negative effect, it is necessary to add a coefficient of 1 or less (for example, 0
．． 5) may be output.

FIG. 9(a) shows the movement of the magnetic head when the track runout Y is ±10 μm. FIG. 9(a) shows the magnetic head 3 and the optical sensor when no notch filter is included in the control circuit. The track following characteristics are shown when a 10% difference is provided between the position-voltage conversion coefficients of No. 5. Figure 9 (
b) is an example in which a notch filter 26 is inserted under the same conditions.

As can be understood from the figure, by including the notch filter 26, specific frequency components can be suppressed, and side effects of estimation errors can be suppressed. Also,
Since the movement of the magnetic head 3 between the zumbling periods is utilized, the disturbance characteristics are improved.

In the above embodiment, an example was explained in which the displacement of the head moving mechanism 4 is detected by the optical sensor 5, but this displacement can also be detected by other sensors such as a magnetic sensor or an electric sensor such as a capacitance type. It can also happen.

Further, in the above embodiment, an example was explained in which one estimated position error signal is inserted between sectors, but two or more estimated values may also be inserted.

Furthermore, in the above embodiment, an analog notch filter is used to reduce the influence of the estimation error on the estimation error signal E2(S), but this effect can also be obtained using a low-pass filter or a digital filter. I can do it.

7 ] 8 In short, the present invention can be implemented in various modifications without departing from the gist thereof.

〔Effect of the invention〕

As described in detail above, according to the present invention, the magnetic head can be moved to the track even if track wobbling occurs, without significantly increasing the number of servo sectors, that is, without causing a decrease in the storage capacity of recorded and reproduced data. can be tracked efficiently and with high precision. Furthermore, since the movement of the magnetic head between sampling periods is utilized, the disturbance characteristics are improved, and its practical effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an overview of a head positioning device of the present invention, FIG. 2 is a block diagram showing an example of the configuration of a magnetic disk head positioning device according to an embodiment of the present invention, and FIG. 3 is a block diagram showing an example of the configuration of a magnetic disk head positioning device according to an embodiment of the present invention. FIG. 4 is an explanatory diagram showing the configuration of the servo sector on the medium, FIG. 4 is an explanatory diagram showing the configuration of the servo sector and servo pattern, FIG. 5 is an explanatory diagram showing the reproduced signal, and FIG. 6 is an explanatory diagram showing the control system in the above embodiment. A block diagram showing the model, FIG. 7 is an explanatory diagram of the track shape as track runout information, FIG. 8 is an explanatory diagram of the head operation, and FIGS. 9(a) and 9(b) are diagrams showing the track following characteristics. FIG. 2...Magnetic disk medium 3...Magnetic head 4...Movement mechanism 8D, 8G...Servo sector 20M...RAM (track runout information storage unit) 26.
... Notch filter El (S) ... Position error signal E2 (S) ... Estimated error signal

Claims (8)

[Claims] (1) A magnetic disk that guides the magnetic head along a predetermined track while reading servo information provided in each sector with a magnetic head on a large number of tracks provided on the circumference of a rotationally driven magnetic disk medium. In the head positioning device, there is provided a track runout information storage means for storing in advance the deviation of the track with respect to the rotation axis center as track runout information; a positioning means for positioning the magnetic head on a predetermined track; a current position detecting means for detecting the current position of the magnetic head; and a means for the magnetic head to read servo information of the next sector from track runout information in the storage means. a truck position estimating means for estimating the actual position of the truck; and an estimation error signal forming means for forming an estimated error signal from the difference between the truck position estimated by the means and the current position detected by the current position detecting means. A head positioning device for a magnetic disk, comprising intermediate signal providing means for giving the estimated error signal formed by the means as a position error signal of the positioning means in the middle of each sector. (2) In the head positioning device for a magnetic disk according to claim 1, the positioning means sets the number of estimated error signals given by the intermediate signal giving means in the middle of each sector to be (N+1)/ A head positioning device for a magnetic disk, comprising means for suppressing twice the frequency component. (3) The magnetic disk head positioning device according to claim 1, wherein the track runout information is track shape information about a specific track detected when the magnetic disk medium is rotated once. Disk head positioning device. (4) In the magnetic disk head positioning device according to claim 3, the detection of the track shape information is performed at the time of loading the medium or periodically, and is also performed automatically using free time during data recording and reproduction. A magnetic disk head positioning device characterized in that: (5) In the magnetic disk head positioning device according to claim 3, the detection of the track shape is obtained from servo information of each servo sector regarding a specific track when the magnetic head is fixed and the disk is rotated once. A magnetic disk head positioning device characterized by the following. (6) In the magnetic disk positioning device according to claim 3, the track shape is detected from the detection value of the current position detecting means when the magnetic head follows a specific track and the disk is rotated once. A magnetic disk positioning device characterized in that: (7) In the magnetic disk head positioning device according to claim 3, the specific track is provided in a guard zone, and the guard zone is provided with more servo sectors than the data zone. head positioning device for magnetic disks. (8) A magnetic disk medium of a servo sector type having a guard zone and a data zone, characterized in that the number of sectors in the guard zone is greater than that in the data zone.