JP2003338145A - Apparatus for simultaneously detecting position and speed of magnetic head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably achieve high positioning precision with a low sampling rate by simultaneously detecting a position and a speed from one servo zone, and performing a position feedback and speed feedback as a servo system. <P>SOLUTION: Three patterns are prepared as a servo pattern, i.e., a clock pattern 13 wherein line patterns orthogonally crossing with a disk peripheral direction are arranged at fixed interval, an R pattern 14 wherein the line patterns inclined by +θ with respect to the clock patterns are arranged at fixed interval, and an L pattern 15 wherein the line patterns inclined by -θare arranged at fixed interval and also whose number is the same as that of the R patterns. The position of a head is obtained by a phase difference among a clock burst signal obtained from the clock patterns, an R burst signal obtained from the R patterns and an L burst signal obtained from the L patterns. The speed is obtained from a frequency deviation between the R burst signal and the L burst signal. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for simultaneously detecting the position and speed of a magnetic head.

[0002]

2. Description of the Related Art FIG. 7 is a schematic block diagram of a tracking servo system of a hard disk drive 100 and a magnetic disk 1.
It is a figure which shows the schematic map of the servo pattern 104 recorded on 01. As shown in FIG. 7, in the bird disk device 100, position information for detecting the relative position between the target track 102 and the magnetic head 103 on the built-in magnetic disk 101 (this is the servo pattern 104).
Is recorded on the magnetic disk 101.

As shown in FIG. 7, the spindle motor 10
5, the magnetic disk 10 rotated at several thousand revolutions per minute
Sectors 106 each including a zone in which a servo pattern 104 is recorded and a zone in which data is recorded / reproduced are alternately arranged on the magnetic disk 1 at a constant interval in the circumferential direction of the track. Medium, passing the zone where the servo pattern 104 is recorded at regular intervals,
It can detect its own position (this method is called a sector servo method and is widely used in the hard disk device 100). The servo demodulation circuit 107 is a circuit for obtaining a position error signal 109 based on the servo burst signal 108 detected by the magnetic head 103 from the servo pattern 104, and the servo controller 110 makes the position error signal 109 small. Further, it is a unit for calculating the drive current 112 to the head actuator 111.

FIG. 8A is an example of a conventional servo pattern recorded in a servo zone. Clock pattern 113 for recovering the servo clock, and A phase pattern 114 and B phase pattern 1 for detecting the position
It consists of fifteen. Track spacing W is A sleeve pattern 11
4, Equal to the radial repeat length of the B-phase pattern 115.
FIG. 8B shows the magnetic layer magnetic flux distribution of the magnetic disk 101 and the servo burst signal 108 to be reproduced when the magnetic head 103 follows the locus T0. FIG. 8C shows the magnetic head 1.
03 traces the locus T1 (= target track) and the magnetic layer magnetic flux distribution of the magnetic disk 101 and the reproduced servo burst signal 108. FIG. 8D shows the magnetic field when the magnetic head 103 traces the locus T2. The magnetic flux distribution of the magnetic layer of the disk 101 and the reproduced servo burst signal 108.

The clock burst signal 1 reproduced from the clock pattern 113 by the locus of the magnetic head 103.
No. 16 does not change, but the amplitudes of the A-phase burst signal 117 reproduced from the A-phase pattern 114 and the B-phase burst signal 118 reproduced from the B-phase pattern 115 change.
If the amplitude values of the A-phase burst signal 117 and the B-phase burst signal 118 are peak-held, and the amplitude values are VA and VB, respectively, the positional deviation of the magnetic head from the target track can be detected by (VA-VB). . As the actual position shift signal, (VA-VB) is changed to (VA + VB)
Normalize with and output. Detection range is track interval W
The position deviation exceeding the track interval W is grasped by counting the number of tracks.

FIG. 9 is a schematic block diagram of a servo demodulation circuit 107 for obtaining a position signal from a servo burst signal.
A PLL block 119 that generates a servo clock from the clock burst signal 116 by a PLL (Phase Locked Loop) process, and an A-phase burst signal 1
17 is peak-held, its amplitude VA is determined and the A-phase peak hold block 120 for synchronous output is peak-held, and the B-phase burst signal 118 is peak-held, and its amplitude VB is determined, and the B-phase peak hold block 12 is synchronously output.
1, VA, VB to position signal (VA-VB) / (VA +
VB) linear operation block 122, enable signal generation block 123 that outputs enable signals for the A-phase peak hold block and B-phase peak hold block
Consists of.

[0007]

The hard disk drive employs a sector servo system and detects the position of the magnetic head for each sector. In order to realize high gain positioning servo control only by position feedback, it is necessary to increase the frequency of position detection and reduce the sampling error of position detection. A high-speed detection circuit is indispensable, and the intervals between the servo zones need to be narrowed, that is, the number of servo zones needs to be increased, and the capacity of the data zone used by the user also decreases.

On the other hand, when both position feedback and velocity feedback can be applied, high gain servo control can be realized at a lower sampling rate than in the case of only position feedback. This is because the velocity feedback has the effect of improving the damper performance and the stability of the servo system.

However, the conventional servo pattern is for detecting the average relative position between the target track and the magnetic head when passing through the servo zone. When the head is tilted from the circumferential direction, that is, even if the magnetic head has a certain velocity in the disk radial direction, the magnetic head can detect from the servo pattern detection of each servo zone is the averaged relative It is only the position, and detection of the velocity component is not assumed. In order to detect the velocity component, there is no choice but to obtain it from the difference with the position signal in the adjacent servo zone, and in order to obtain the velocity with high accuracy, it is essential to increase the detection frequency after all. Japanese Patent Laid-Open No. 2000-123506 is disclosed as a related conventional technique. In this conventional technique, three patterns must be set in one sector and different pattern combinations must be used for position detection and speed detection, and therefore complicated detection processing must be performed.
There is a problem that the circuit for that is also complicated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic head position / velocity simultaneous detection apparatus which solves the above problems.

[0011]

In order to solve the above-mentioned problems, the invention of claim 1 is a magnetic disk in which sectors each having a servo pattern recording zone and a zone for recording / reproducing data are arranged at regular intervals. In a hard disk drive for driving a magnetic disk, a relative position and a relative position of the magnetic head with respect to a target track on the magnetic disk based on a detection signal from the magnetic head that has detected a servo pattern of each sector on the magnetic disk being driven. Each servo pattern of the magnetic disk comprises a clock pattern in which line patterns orthogonal to the disk circumferential direction are arranged at regular intervals, and + θ (θ) with respect to the clock pattern. <90
The R pattern has a plurality of line patterns inclined at a constant interval and the line patterns inclined at -θ have the same number as the R pattern at a constant interval. The detection means, based on the clock burst signal obtained from the detection signal of the clock pattern, the R burst signal obtained from the detection signal of the R pattern and the L burst signal obtained from the detection signal of the L pattern.
It has a position detecting means for obtaining the position of the magnetic head from the phase difference from the burst signal, and a speed detecting means for obtaining the speed of the magnetic head from the frequency changes of the R burst signal and the L burst signal. And

According to a second aspect of the present invention, in the first aspect, the speed detecting means directly Fourier transforms the frequency changes of the R burst signal and the L burst signal into the R burst signal and the L burst signal. It is characterized in that the speed of the magnetic head is obtained by using the detected result.

According to a third aspect of the present invention, in the first aspect, the speed detecting means determines the frequency change of the R burst signal and the L burst signal by the continuous length of the R burst signal and the continuation of the L burst signal. Is detected as a change in length, and the speed of the magnetic head is obtained based on the two detected lengths.

[0014]

FIG. 6 is a schematic block diagram of a tracking servo system of a hard disk device 10 according to an embodiment of the present invention. The structure of the hard disk device 10 other than the magnetic disk 1 is the same as that of the hard disk device 100 of FIG. Therefore, the internal configurations of the servo demodulation circuit 7 and the servo controller 9 are different from those of FIG. 2 is the target track, 3
Is a magnetic head, 4 is a spindle motor, and 5 is a head actuator.

FIG. 1A shows an example of the servo pattern of the present invention recorded on the magnetic disk 1. A line pattern orthogonal to the circumferential direction of the magnetic disk 1 is
A clock pattern 13 arranged at a constant interval, an R pattern 14 in which a plurality of line patterns inclined by + θ with respect to the clock pattern 13 are arranged at a constant interval, and a line pattern inclined by −θ with respect to the clock pattern 13. Consist of L patterns 15 arranged in the same number as the R patterns 14 at regular intervals. The clock pattern 13 is for generating a servo clock as in the conventional example, and the R pattern 14 and the L pattern 15 indicate the relative position and relative speed of the magnetic head 3 to the target track 2 on the magnetic disk 1. It is for detection.

First, a position detecting method (refer to FIG. 5 for position detecting means) when the locus of the magnetic head 3 moves parallel to the radial direction of the magnetic disk as shown in FIG. 1A will be described. . FIG. 1B shows the magnetic layer magnetic flux distribution of the magnetic disk 1 and the servo burst signal 8 to be reproduced when the magnetic head 3 follows the locus T1, and FIG. 1C shows the case where the magnetic head follows the locus T2. , Magnetic disk 1
The magnetic flux distribution of the magnetic layer and the reproduced servo burst signal. The clock burst signal 16 reproduced from the clock pattern 13 shows no difference, but the R burst signal 17 reproduced from the R pattern 14 and the L burst signal 18 reproduced from the L pattern 15
It can be seen that the phase is shifted although the frequency does not change. When the radial repeating length of the R pattern 14 or the L pattern 15 is Z, the phase shift amount is Z.
By multiplying by / 2π, the relative position x of the magnetic head 3 with respect to the target track 2 can be detected. As the phase shift detecting means, for example, U.S.P. S. Pate
ntNo. 4, 549, 232, etc.

Next, as shown in FIG. 2A, the magnetic head 3
A method of detecting the inclination angle α will be described when the locus of is inclined by α with respect to the circumferential direction. As will be described later, if the inclination angle α is known, the radial moving speed of the magnetic head 3 can also be known.

FIG. 2B shows the magnetic flux distribution of the magnetic layer of the magnetic disk 1 when the magnetic head follows the locus T1 and the reproduced servo burst signal. FIG. 2B shows the case where the magnetic head follows the locus T2. The magnetic flux distribution of the magnetic layer of the magnetic disk 1 and the servo burst signal 8 to be reproduced. There is no difference in the clock burst signal 16 reproduced from the clock pattern 13, but the frequency changes in the R burst signal 17 reproduced from the R pattern 14 and the L burst signal 18 reproduced from the L pattern 15. I understand that In the example of FIG. 2C, the frequency of the R burst signal 17 is low and the frequency of the L burst signal 18 is high.

The amount of change in the frequency will be considered with reference to FIGS. It is assumed that the R pattern 14 is inclined by θ with respect to the clock pattern 13, and the locus of the magnetic head 3 is inclined by −α from the disk circumferential direction (see FIG. 3). Letting WR be the distance in the disk circumferential direction and h be the distance in the disk radial direction when the head locus extends from the left end to the right end of the line pattern, h = WR × tan α = (WR−W) × tan (π / 2−θ) ...... becomes. Therefore, 1 / WR = (1-tan θtan α) / W.

On the other hand, it is assumed that the L pattern 15 is inclined by −θ with respect to the clock pattern 13. As with the R pattern 14, the locus of the magnetic head 3 is assumed to be inclined by -α from the disk circumferential direction. Letting WL be the distance in the disk circumferential direction and h is the distance in the disk radial direction when the head locus goes from the left end to the right end of the line pattern, h = WL × tan α = (W−WL) × tan (π / 2−θ) ...... becomes. Therefore, 1 / WL = (1 + tan θtan α) / W. From the formula, W = 2 × (1 / WL + 1 / WR) ⁻¹ tanα = (W / 2tanθ) × (1 / WL−1 / WR) = cotθ × (WR−WL) / (WL + WR) …… Magnetic The rotation speed ω of the disk 1 is constant. Assuming that the measured radial position on the magnetic disk 1 is r, tan α = Δx / (rωΔt) (since Δ represents a minute fluctuation amount), the velocity v is v = ΔX / Δt = r ω · tan α = r · ω · cot θ × (WR−WL) / (WL + WR) ... That is, the inclination angle α of the head locus is r, ω, θ and WR,
It can be obtained from WL. r, ω, and θ are known. When the frequency of the R burst signal 14 is fR and the frequency of the L burst signal 15 is fL, WR and WL are expressed as follows. WR = 1 / (2fR) ... WL = 1 / (2fL) ... (10) fR and fL are the R burst signal 14 and the L burst signal 1
5 can be obtained by performing a Fourier analysis. At this time, the speed v is expressed as in Expression (11). v = r · ω · cot θ × (fL−fR) / (fR + fL) (11) Instead of fR and fL, from the continuous time tR of the R burst 14 and the continuous time tL of the L burst 15 in FIG. You can also ask. At this time, WR and WL are WR = ω × tR × R number of patterns × 2 (12) WL = ω × tL × L number of patterns × 2 (13), so v = r · ω · cotθ X (tR-tL) /
(TL + tR) (14). The servo demodulation circuit
It is only necessary to obtain the continuous time of the R burst signal 14 and the L burst signal 15 and perform a simple calculation based on the equation (14).

FIG. 5 is a schematic block diagram of the servo demodulation circuit 7 of the present invention for realizing the above-described position and velocity detection method. The servo demodulation circuit 7 uses a PLL (Ph
a PL for generating a servo clock from the clock burst signal 16 by the "ASE Locked Loop" process.
From the L block 19, the R burst signal 17 and the servo clock, the clock burst signal 16 and the R burst signal 1
The amount corresponding to the phase difference of 7 is obtained, and the R phase detection block 20 for synchronous output, the L burst signal 18 and the servo clock are used to determine the clock burst signal 16 and the R burst signal 1.
An amount corresponding to the phase difference of 8 is obtained, and the outputs of the L phase detection block 21 and the R phase detection block 20 for synchronous output are
A linear operation block 24 for averaging the output of the phase detection block 21 and converting it from the phase dimension to the position dimension by multiplying Z / 2π, Fourier transforming the R burst signal 17 to obtain the frequency fR, and synchronously outputting it. Frequency detection block 2
2. Fourier transform of L burst signal 18 to frequency fL
L frequency detection block 23, f
From R and fL, the velocity signal r.ω.cotθ × (fL-f
R) / (fL + fR), a linear operation block 2
5, R phase detection block 20, L phase detection block 2
1, an enable signal generation block 26 for outputting enable signals for the R frequency detection block 22 and the L frequency detection block 23. In the linear operation block 24, 24A is an adder, 24B is a 1/2 multiplier, and 24C.
Is a Z / 2π multiplier, and in the linear operation block 25, 25A and 25B are adders, 25C is a divider, and 25D.
Is an r · ω · cot θ multiplier.

Instead of the R frequency detection block 22, R
A block for obtaining the continuous time tR of the burst signal, L
Instead of the frequency detection block 23, a block for obtaining the continuous time tL of the L burst signal may be used.

[0023]

As described above, according to the present invention,
Since the position and the velocity can be detected simultaneously from one servo zone, not only the position feedback but also the velocity feedback can be easily applied to the servo system, and stable and high positioning accuracy can be realized even at a low sampling rate.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a servo pattern of the present invention and position detection by the servo pattern.

FIG. 2 is a schematic explanatory diagram of a servo pattern of the present invention and speed detection by the servo pattern.

FIG. 3 is a diagram illustrating the principle of speed detection in the R pattern of the present invention.

FIG. 4 is a diagram illustrating the principle of speed detection in the L pattern of the present invention.

FIG. 5 is a block diagram of a servo demodulation circuit according to the present invention.

FIG. 6 is a block diagram of a tracking servo system of the hard disk device of the present invention.

FIG. 7 is a diagram showing a tracking servo system of a conventional hard disk device and a servo pattern of a magnetic disk.

FIG. 8 is a schematic explanatory diagram of a conventional servo pattern and position detection by the servo pattern.

FIG. 9 is a diagram of a conventional servo demodulation circuit.

[Explanation of symbols]

1 magnetic disk 2 target truck 3 magnetic head 4 spindle motor 5 head actuator 7 Servo demodulation circuit 8 Servo burst signal 9 Servo controller 10 Hard disk drive 13 clock patterns 14 R pattern 15 L pattern 16 clock burst signal 17 R burst signal 18 L burst signal 19 PLL blocks 20 R phase detection block 21 L phase detection block 22 R frequency detection block 23 L frequency detection block 24 Linear operation block 25 Linear operation block 26 Enable Signal Generation Block

Claims (3)

[Claims] 1. A hard disk drive for driving a magnetic disk, in which sectors each having a servo pattern recorded zone and a zone for recording / reproducing data are arranged at regular intervals, in a sector of the magnetic disk being driven. Based on a detection signal from the magnetic head that has detected the servo pattern, a simultaneous detection means for simultaneously detecting the relative position and the relative speed of the magnetic head with respect to the target track on the magnetic disk is provided, each servo pattern of the magnetic disk Is a clock pattern in which line patterns orthogonal to the disk circumferential direction are arranged at regular intervals, and a plurality of line patterns inclined by + θ (θ <90 °) with respect to the clock patterns are aligned at regular intervals. The R pattern and the line pattern inclined by-? And a same number only alongside L pattern, said co-detecting means, based on the clock burst signal obtained from the detection signal of the clock pattern, the R
Position detecting means for determining the position of the magnetic head from the phase difference between the R burst signal obtained from the pattern detection signal and the L burst signal obtained from the L pattern detection signal; and the R burst signal and the L burst. A device for simultaneously detecting the position and speed of a magnetic head, comprising: speed detection means for obtaining the speed of the magnetic head from a frequency change of a signal. 2. The speed detection means according to claim 1, wherein the R burst signal and the L burst signal are used.
Simultaneous detection of the position and speed of the magnetic head, characterized in that the speed of the magnetic head is obtained by using the result of direct Fourier transform of the R burst signal and the L burst signal for detecting the frequency change of the burst signal. apparatus. 3. The speed detection means according to claim 1, wherein the R burst signal and the L burst signal are used.
A frequency change of the burst signal is detected as a change in continuous length of the R burst signal and a continuous length of the L burst signal, and the speed of the magnetic head is obtained based on the detected two lengths. Characteristic magnetic head position and velocity simultaneous detection device.