JPS6369078A - Servo method in disk type recording and reproducing device - Google Patents

Abstract

PURPOSE:To perform positioning without using a position sensor by obtaining the number of tracks passed from a sector immediately preceding to a present sector and a head speed, and accumulating the number of tracks from the time of starting seek to the present sector. CONSTITUTION:The reproducing signal of an R/W head 1 is supplied through a reproducing amplifier 2 to a servo signal detecting circuit 3. The circuit 3 detects the reproducing waveform level of an embedded servo signal and by a signal processing circuit 4, a sawtooth servo signal is formed. Next, a processor 5 obtains respectively the number of tracks where the head 1 has passed, the speed of the head 1 and off track information and supplies them to an actuator control circuit 7. The circuit 7 controls an actuator 8 such as a voice coil and positions the head 1. Consequently, the information necessary to positioning is obtained from its own servo signal and the sensor for detecting the position can be made unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a servo method for moving a R/W head to a target track in, for example, a hard disk drive.

[Summary of the invention]

' In this invention, the head is operated under the condition that the acceleration during movement is smaller than a predetermined value, and has a value corresponding to the position of the head on each track with the repetition period of the sector-shaped embedded servo signal. A servo signal is formed,
The number of tracks passed from the previous sector to the current sector and the speed of the head are calculated based on the servo signal of the previous sector and the servo signal of the current sector, and the number of tracks from the start of the seek operation to the current sector is accumulated. By calculating the number of tracks passed through, the speed, and the off-track axis necessary for the servo can be obtained from the servo signal alone.

[Conventional technology]

In conventional hard disk drives, the following is known as a servo system for positioning the R/W head on a target track.

One method is to use one disk surface among a plurality of disk surfaces exclusively for positioning. That is,
An embedded servo signal is recorded on the entire surface of this disk surface, and the embedded servo signal is always read.The read embedded servo signal determines the position of each R/W head relative to other disk surfaces. is controlled.

In this method, if there is a misalignment between the center of the embedded servo signal recorded on the servo disk surface and the center of the track on the data disk surface, there will be a difference between when writing data and when reading data. There is a problem with off racks. Furthermore, since a dedicated disk surface for the servo is required, there is a drawback that the cost increases.

Other conventional servo systems use optical sensors for coarse positioning and embedded servo signals for fine positioning. In other words, R/W on one side of the forked arm.
A head is provided, and an optical sensor is provided on the other side, and the position of the R/W head is detected by the optical sensor.

[Problem that the invention seeks to solve]

However, it is necessary to increase the precision and mounting precision of the optical sensor, and thermal off-track occurs due to expansion and contraction of the arm or disk due to changes in temperature conditions. Precise positioning using embedded servo signals
This is possible as long as off-track does not exceed (TP/2). Therefore, the above thermal off track is (TP/2
), positioning becomes impossible and track deviation occurs. Furthermore, as mentioned above, providing a separate position sensor increases cost.

Therefore, an object of the present invention is to provide a servo method for a disk type recording/reproducing apparatus that does not require a position sensor even when using an arm such as a voice coil motor that cannot perform positioning by itself.

[Means for solving problems]

In this invention, in a servo method for a disk type recording/reproducing device in which an embedded servo signal is recorded in sectors along with data on the same disk surface, the acceleration or deceleration when the head moves in the radial direction of the disk is 1αI. <0.5 (Ts/TP) (However, TP:
I-rack pitch, Ts: repetition period of the embedded servo signal), and a servo signal with a value corresponding to the position of the head on each track is formed with the repetition period Ts, and is synchronized with the servo signal of the previous sector and the current one. A servo method that calculates the number of tracks passed from the previous sector to the current sector and the head speed based on the servo signal of the sector, and then accumulates the number of tracks from the start of the seek operation to the current sector. be.

[Effect]

In a state where the acceleration or deceleration when the R/W head moves is limited, it is known how many tracks it passes from the (τ-1)th sector to the τth sector. Further, the distance traveled from the (τ-1)th sector to the τth sector is known, and the number of tracks passed per sector, that is, the speed V is known. Furthermore, since the servo signal itself has a value corresponding to the position of the head on each track, off-track information for fine servo can be obtained from the servo signal. Therefore, the information necessary to position the R/W head on the target track (number of tracks passed, speed V, off-track information) can be obtained from the servo signal itself, making it possible to eliminate the need for a sensor for position detection.

[Example] An example of the present invention will be described below. Figure 1 shows
1 is a diagram of an example of a hard disk drive to which the present invention is applied. In FIG. 1, l indicates an R/W head, and an arm to which this R/W head 1 is attached is driven by a voice coil motor. A reproduction signal from the R/W RAD 1 is supplied to a servo signal detection circuit 3 via a reproduction amplifier 2. A sector servo method is used in which embedded servo signals are written in each sector of each track of a hard disk. Further, a tri-bit pattern is used as an embedded servo signal. The servo signal detection circuit 3 detects the level of the reproduced waveform of this embedded servo signal.

The output signal of the servo signal detection circuit 3 is supplied to the signal processing circuit 4. This signal processing circuit 4 generates a servo signal that changes in a sawtooth waveform in response to a change in the position of the R/W head 1 (or the arm on which the R/W head 1 is installed) from the output signal of the servo signal detection circuit 3. It is formed. Servo signals from the signal processing circuit 4 are supplied to the processor 5.

The processor 5 performs signal processing according to the present invention,
Number of tracks passed by R/W head 1, R/W head 1
The speed and off-track information of the vehicle are determined respectively.

Servo information regarding these R/W heads 1 is supplied to a seven-actuator control circuit 7, and a control signal for driving an actuator 8 is formed. The actuator 8 is, for example, a voice coil. The actuator control circuit 7 is provided with a CPU, from which speed profile data is output, and information about the number of moving tracks, speed, and position is sent to the CPU.
Supplied to U.

In the present invention, the processor 5 can detect the moving distance (track count), the moving speed, and off-track information using only the embedded servo signal from the R/W hand l.
B The formation of the embedded servo signal and the sawtooth servo signal will be explained with reference to FIG.

FIG. 2A shows an enlarged view of a part of the track pattern formed on one surface of one disk, and the vertical direction indicated by the arrow R in FIG. 2A indicates the rotational direction of the disk, and the arrow S The horizontal direction indicated by indicates the scanning direction of the R/W head l, and CI, C2, C3, . . . indicate the center of the data track, respectively.

For example, a data track formed in concentric circles is divided into 64 sectors at equal angular intervals, and embedded servo signals A1. Bl and A2°B2 are recorded in advance. In the track pattern shown in FIG. 2A, R
The track width TW and track pitch TP of the /W head l are made equal, and therefore the embedded servo signals Al and B1, in which no guard band area exists, are repeatedly recorded at a pitch and phase that match the data track. The embedded servo signal A2.82 is recorded in a pinch that coincides with the data track, and is also recorded with a phase shift of TP/2.

A dry focus pattern is used as the embedded servo signal. The embedded servo signal will be explained with reference to FIG. If the embedded servo signals AI and A2 are called the A pattern, and the embedded servo signals Bl and B2 are called the B pattern, when the R/W RAD 1 reproduces the A pattern without any deviation, the waveform shown in FIG. 2A is generated. When the R/W hand 1 reproduces the B pattern without deviation, a reproduced signal having the waveform shown in FIG. 2B is obtained. The reproduced signals of the A pattern and the B pattern each include a positive pulse signal P1 that is generated at regular intervals. In the reproduction signal of the A pattern, a negative pulse signal P2 is generated at a timing delayed from the pulse signal P1 for a period (⅓) of the period defined by the pulse signal P1. B
In the pattern reproduction signal, a negative pulse signal P3 is generated at a timing delayed from the pulse signal P1 for a period of (2/3) of the period defined by the pulse signal P1.

When the R/W head 1 is just scanning over pattern A or pattern B, only the pulse signal P2 is generated in the reproduction signal of pattern A, and the pulse signal P2 is generated in the reproduction signal of pattern B.
Only pulse signal P3 is generated. Also, A pattern and B pattern
When the R/W hand l scans a position midway between the two patterns, both pulse signals P2 and P3 of equal amplitude are obtained, as shown in FIG. 2C. Since the embedded servo signal is a signal in which patterns A and B are recorded alternately, the amplitude a of the pulse signal P2 and the amplitude a of the pulse signal P3
The relative relationship with the amplitude corresponds to the scanning position of the R/W head 1.

Corresponding to the track pattern shown in Figure 2A, the horizontal axis is R/
When the head position of the W head 1 is assumed, the amplitude a of the embedded servo signal At changes as shown by the solid line in FIG.
It changes as shown by the broken line in Figure B. In addition, the amplitude a of the embedded servo signal A2 and the embedded servo signal B
The amplitude b8 of 2 changes as shown by the solid line and the broken line, respectively, in FIG. 2C. These embedded servo signals are processed as follows to form a sawtooth servo signal r(B) shown in the second diagram.

Another method for forming the servo signal r(1) having a sawtooth-like value change when (at ≧b+) and (al <b,) is as follows: (a, ≧b).

), extract the change in amplitude b2 and find (al<b+
), a method of extracting the change in amplitude a may be used.Also, as a pattern of embedded servo signals to obtain such a servo signal f(t), the second
Others than those shown in Figure A can be used.

The meaning of the graph of the servo signal shown in the second diagram above.

The point is that the value obtained when the R/W head 1 passes through a certain sector servo area is on this graph.
This does not mean that such a waveform position information output can be obtained when the R/W head 1 is moved. The servo signal is always temporally discontinuous data obtained at each sector interval. For example, the number of sector servos is (64 sectors/1 rotation), and the rotational speed of the disk is 3600 (rpm).
), the sector interval is approximately 260 (μsec).

In addition, the above-mentioned sawtooth wave-like servo signal outputs the same data for every l track pitch TP, and also outputs a value from 0 to 1 that is proportional to the position of the R/W head 1 in l track pinch TP. The time when 0.5 is output is the track center, and the current R/
W Herad 1's position relative to the track center is %T
Obtained with PO dynamic range. Figure 4 shows changes in the servo signal within the n-th track.The position Sl where the servo signal value becomes O is the boundary between the (n-1)th track and the n-th track, and the servo signal changes within the n-th track. The position S2 where the signal value is 0.5 is the center of the n-th track, and the position S3 where the servo signal value is 1 is the boundary between the n-th track and the (n+1)th track.

As mentioned above, since the servo signal indicating the position of the R/W RAD 1 is discrete data for each sector interval (approximately 260 μsec), the time axis t is quantized by the sector interval τ. Sector interval τ is a positive integer, (τ−〇)
The seek operation starts when .

This invention uses only the servo signal, which is discrete data as described above, to count the number of moving tracks when the R/W head 1 (arm) is moved, detect speed, and obtain off-track information for on-track fine servo. Seek everything. For this process, the following limits are set on the maximum values of acceleration and deceleration of the R/W head l.

1αl<0.5 (Ts/Tp) 1α1: Maximum value of acceleration or deceleration, TP Nidrak pitch, TS: Repetition period of servo pattern R/W The speed of the head l generally follows the speed profile shown in Figure 5. controlled. The period immediately after the start is an acceleration region 11 in which the speed V increases, then an equal distance region 12 in which the speed V is constant, and when approaching the target track, the acceleration region 11 increases.
．． The speed V is reduced to a zero range 13, the on-track fine servo operates near the target track, and the R/W head 1 stops on the target track. The number of moving tracks and the speed 1 position of the R/W head 1, that is, the actuator 8, are detected from the servo signal, and the servo operation is performed according to the speed profile. The maximum value of acceleration 1α1 is acceleration region 1
Occurs at 1. For example, 20000 after 10 (msec)
In the case of uniform acceleration motion such as () rack/5ee), 1α1≦0.137 () rack/sector t).This inequality indicates that the speed of the R/W head 1 increases while moving one sector. The maximum increase or decrease is 0.137 (track/sector), which means that it will not change any more rapidly.

First, a method for determining the number of moving tracks n from the servo signal f (τ) will be explained.

y−F(τ)・TP (F (0) = 0.5) (F
(τ)·TP: position when passing the τth sector from the start of arm movement) is defined as follows. This can be further expressed as a combination of the integer part and the decimal part: F(τ)=n+f(τ) (0≦f (τ)<1) (r! integer). f(τ) is the servo signal itself, and n is the number of tracks passed (more precisely, the number of boundaries between tracks, which is positive).

Negative indicates direction. ), and finding the number of moving tracks n when r (τ) is known is nothing but counting the number of tracks passed from the servo signal.

Next, y=G(τ)・TP −(F(τ)−F(τ−1))・TP(G(τ)
・TP): Defined as the distance traveled from the (τ-1)th sector to the τth sector), then G(τ
) can also be expressed as a combination of the integer part and the decimal part as follows: G(τ)=τ0g(τ) (05g(τ)<1) (Kτ: integer).

Now, considering the relationship between g(τ) and f(τ), ■f
When (τ)≧f (τ−1), g(τ)=f (τ)−f (τ−1) ■ f(τ) × f
(τ-1), g (τ)=f (τ)-f (τ-1)+1.

In this case, a carry (+1) occurs when the decimal part becomes negative.

The number mτ of tracks passed from the (τ-1)th sector to the τth sector is Kτ or (Kτ+1)
Either. Then, f (τ−1) has g(τ)(
When the sum of 0≦g(τ)<l) exceeds 1, (m
τ=to τ+1), and of course C! (τ)kuf (τ
-1)), so.

Next, let's find τ. A graph of the relationship between G(τ) and g(τ) is shown in FIG. As described above, since a limit is set on the maximum acceleration 1α1, it always takes a period of 7 sectors or more for G(τ) to change by one track.

Consider h(τ)=g(τ)−g(τ−1).

■When τ−, = τ, α≦h (τ)≦α ■When τ−, + 1 = τ, α≦(g (τ) +1) −g (τ−1)≦
α−α−1≦h(τ)≦α−1 ■When τ−+1=τ, α≦(g (τ) −1) −g (τ−1)≦
Since there is a limit of α-α+1≦h (τ)≦1+α ■[1αl #0.137() rack/sector 2)], (τ in Kτ-1+2≦) or (Kτ
-3-2≧τ) cannot occur, therefore, ■
The reverse of the relationship ■■ also holds true.

The possible values of h(τ) for the relationship between 1(r- and τ) can be expressed on a number line as indicated by diagonal lines in FIG. If the maximum value α of acceleration is 1αI<0.5()rack/
As mentioned above, when the relationship of sector 2) is not satisfied,
It cannot be divided into M areas.

In reality, it is necessary to determine 1α1 in consideration of errors in the servo signal.

As described above, since it has been possible to relate the value of τ to each τ, the value of mτ to the value of Kτ, and the value of n to the value of mτ, the number n of tracks passed can be determined.

FIG. 8 is an example of a flowchart for determining the number n of tracks passed from the servo signal.

In this flowchart, (g′ (τ>−r(τ
)−f (τ−1), and the initial value at the start of the seek operation is Cf (0)=0.5°f (
-1)=0.5. g(0)=0. g(-1)=0,
τ≧O].

In the flowchart shown in FIG. 8, in step ■, it is determined whether g'(τ) is positive or not.
) is positive, g(τ) = g'(τ), (step ■), and when g''(τ) is negative, (g (τ) = g
′ (τ) + 1) (step ■) 0th order, then h(
It is checked which range τ) (=g(τ)-g(τ-1) is included in as shown in FIG. 7 (steps ① and ①).

When (h(τ)>0.5), (τ-1-1 to Kτ-
) (step ■). When (h (τ)<0.5), (Kτ=τ−++1) (step ■), and when (−0,5≦h(τ)≦0.5), (
Kτ− is set to τ−1).

Next, in steps ①, @l and 0, the number mτ of tracks passed from the (τ-1)th sector to the τth sector is determined. Then, in step @, the number n of tracks passed up to the τth sector is determined.

Furthermore, the speed of the R/W head 1 is determined at step (2) in which g(τ) and τ are determined.

That is, in this example, τ speed information: v=k・(Kτ0g(τ)(k:(1−
Off-track information: If f (τ) is 0 within the target track.
Control so that it becomes 5.

can be obtained only from the servo signals.

In the above embodiment, it is specified that the embedded servo signal has a repetition period Ts of l track pitch TP. However, this repetition period TS is %TP, (2/
3) Various types such as TP and 2TP can be used. When the repetition period Ts is not TP, it is necessary to adjust the obtained number of tracks n corresponding to the repetition Ts''.For example, when (Ts='A T P ), (n=20
), the true number of tracks is (n=10)
becomes.

〔Effect of the invention〕

According to this invention, there is no need for a sensor for detecting the position of the R/W head or arm, and the sensor installation and
! There is no need for JR adjustment, errors due to differences in temperature conditions can be eliminated, and costs can be reduced. In addition, this invention eliminates the need to switch from coarse positioning using the output of a position detection sensor to fine positioning using embedded servo signals, making it possible to perform optimal control toward the true track center from the beginning, eliminating unnecessary settling. It can save time.

[Brief explanation of drawings]

The location is a block diagram of a hard disk drive to which this invention is applied, Figure 2 is a route map used to explain the pattern of embedded servo signals recorded on the disk and the formation of servo signals, and Figure 3 is an example of an embedded servo signal. waveform diagram,
Figure 4 is a partially enlarged view of a servo signal, Figure 5 is an example of a speed profile, Figure 6 is a graph showing the relationship between G(τ) and g(τ), and Figure 7 is a graph showing the relationship between τ-1 and For the relationship of τ, h(
FIG. 8 is a flowchart showing the process for determining the number of tracks passed. Explanation of main symbols in the drawings 1: R/W head, 5: processor, 8: actuator. Agent Patent Attorney Tadashi Sugiura Tomochi λ7 Beraitsu°' 6c Fig.
6 (τ) - Fig. 4 Fig. 5 shows τ - +kK7:n length ↑ 1 h Servo method 3 in disk-type recording and reproducing devices, relationship with the case of the person making the correction Patent applicant address: 6-7-35, Kitashina, Tokyo Parts Store Name (21
8) Sony Corporation CEO Noriyoshi Ohga 4, Agent address: 1-48-10-5 Higashiikebukuro, Toshima-ku, Tokyo, Date of amendment order: November 25, 1986, 6 Specification subject to amendment In column 7 of the brief description of the drawings, in the description of contents of the amendment, page 22, line 13, "position" is corrected to "Figure 1."

Claims (1)

[Claims] In a servo method in a disk type recording/reproducing device in which an embedded servo signal is recorded in sectors along with data on the same disk surface, acceleration or deceleration when a head moves in the radial direction of the disk is provided. If the speed is |α|<0.5(Ts/TP) (however, TP
: track pitch, Ts: repetition period of the embedded servo signal), and with the repetition period Ts, a servo signal having a value corresponding to the position of the head on each track is formed, and the servo signal of the immediately preceding sector is defined as Based on the signal and the servo signal of the current sector, determine the number of tracks passed from the immediately previous sector to the current sector and the speed of the head, and calculate the number of tracks from the start of the seek operation to the current sector. 1. A servo method for a disk type recording/reproducing device, characterized in that the servo method is obtained by accumulating the .