JP2000123506A - Magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the positioning accuracy and the reliability of a write fault signal. SOLUTION: In the magnetic disk device of a sensor servo system, individual servo information is constituted of a pull-in area A, a track identification area B and a position signal/speed detection area C and the position signal/speed detection area C is made to be a constitution consisting of one pair of patterns C-1 and C-3 which are constituted so as to have prescribed azimuth angles of the same phase with respect to the circumferential direction of a track and the pattern C-2 which is held between them. Since the position signal/speed detection area C has the constitution in which phases of patterns C-1 and C-3 are the same phases and the pattern C-2 having the opposite phase is pushed in between them, a servo system detects position information from the phase between the C-1 part and the C-2 part or the C-1 part and C-3 part and detects speed information by observing the phase difference between the C-1 part the C-3 part from one piece of servo information in the same sector. Moreover, the write fault signal for recording is produced from the position information and the speed information in the same sector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive and, more particularly, to a technology effective when applied to position information detection, speed detection, and the like for head positioning in a sector servo system.

[0002]

2. Description of the Related Art In recent years, as a positioning method of a magnetic disk drive, a sector servo method in which a position signal area is intermittently provided in a data plane has become mainstream, and the position signal detection pattern is disclosed in Japanese Patent Application Laid-Open No. 7-45020. A two-phase burst pattern as disclosed in the official gazette and a phase detection pattern as disclosed in Japanese Patent Application Laid-Open No. 7-230676 are used.
From the reproduction output of these patterns, the head position is detected as the amount of deviation from the target position on the disk, that is, as a position error signal. The head is controlled by a servo system to reduce the position error signal. In recent years, as the track density of a magnetic disk device has increased, the positioning accuracy of a head has been improved, and the accuracy of a protect signal (called a write fault) for inhibiting a recording operation when a displacement has occurred due to an external factor such as vibration. Improvement is an important technical issue.

The condition for generating a write fault is determined to occur when the magnitude of the position error signal exceeds a certain value. However, since only about 70 position error signals can be obtained in one round. However, in order to compensate for the influence of the fluctuation of the position signal itself and the amount of position deviation in a data area where there is no position signal, detection of the level of the position signal alone is not sufficient. Impact sensors are also used for light protection, but there were technical issues in terms of sensitivity such as rotational impact.

[0004]

As described above, the technical problems related to the positioning of the magnetic disk drive include an improvement in the accuracy related to the servo system and an improvement in the write fault signal accuracy. To improve the accuracy of the servo system, it suffices to reduce the position error as a result, but the coping method differs depending on the cause. Generally speaking, improving the servo bandwidth is one solution,
Because of the sector servo method, there are limitations on the sampling frequency of the position signal, and limitations on the resonance of the mechanical system, etc., and it may not be possible to easily increase the servo band. Problems when the servo band cannot be raised include insufficient compression of external forces (wind turbulence, bearing viscosity, etc.) acting on the actuator due to insufficient responsiveness and low-frequency gain. In recent small disk drives, the influence of disturbances has been increasing due to the reduction in operating mass, and one of the issues is to improve the compression of low-frequency disturbances. On the other hand, depending on the model, since the rotation speed has been improved, the servo band can be easily improved, and it is important to suppress the mechanism resonance. Further, even if the servo band is the same, the effect may be obtained by compressing the mechanism resonance in order to increase the phase margin.

As an example of speed detection, three patterns are alternately arranged on the head moving path, and the difference between the detected peaks of the first and last patterns and the circumferential time interval between the two patterns are used to determine the radial direction. Japanese Patent Application Laid-Open No. Hei 8-180620 discloses a technique for detecting the actual head speed during a seek without using a track number that may include an error, thereby detecting the head speed. Since the interval between the first and last patterns is narrow, there is a concern that the speed detection accuracy is low for use in generating a write fault signal requiring high accuracy.

An object of the present invention is to provide a magnetic disk drive capable of improving the servo system and improving the write fault signal accuracy.

Another object of the present invention is to provide a magnetic disk drive capable of realizing an efficient speed detection algorithm.

[0008]

According to the magnetic disk drive of the present invention, a velocity signal can be detected simultaneously with a position signal from each of a plurality of servo information areas discretely arranged on data tracks arranged on a magnetic disk. In the servo system, a speed feedback term is provided to compress force disturbance,
For the mechanical system resonance, a loop is provided to obtain the acceleration by the backward difference approximation of the speed and to compress the mechanical system resonance by the acceleration feedback.

In addition, by considering the speed together with the position information, the head trajectory is predicted based on the position and speed information obtained from one servo information area, thereby improving the write fault detection accuracy.

[0010] By constructing an observer using velocity feedback or position and velocity, a force disturbance component is directly included in the control signal, and the force disturbance can be compressed. In addition, the acceleration feedback loop can similarly suppress high-range mechanical system resonance. By considering the speed as well as the position in the write fault signal, the prediction accuracy of the subsequent head trajectory is improved, and the write fault signal level can be determined by estimating the head position in the data area, thereby improving the accuracy.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a conceptual diagram showing an example of the configuration of a servo information area on a magnetic disk in a magnetic disk device according to an embodiment of the present invention. FIG. 2 is a conceptual diagram showing an example of the operation thereof. FIG. 3 is a conceptual diagram of a magnetic disk for explaining an example of the forming method, and FIGS. 4, 5, 6 and 7 are conceptual diagrams showing a modification of the configuration of the servo information area in the present embodiment. It is.

FIG. 8 is a diagram showing an example of a method of generating a write fault signal in the magnetic disk device of the embodiment, and FIG. 9 is an example of a configuration of a servo system in the magnetic disk device of the embodiment. FIG. 10 is a conceptual diagram showing
FIG. 1 is a partially cutaway perspective view showing an example of a configuration of a magnetic disk drive of the present embodiment.

First, an example of the configuration of the magnetic disk drive of the present embodiment will be briefly described with reference to FIG.

As illustrated in FIG. 10, a plurality of magnetic disks 10 are fixed to a common spindle 14 at predetermined intervals in a coaxial and parallel posture, and each of a plurality of recording surfaces of each magnetic disk 10 has A plurality of heads 15 individually held at the distal end of the load arm 11 are set. The base end of the load arm 11 is supported by an actuator 12 that swings about a pivot shaft 12a. The actuator 12 is further driven by a voice coil motor 13. The head 15 is, for example, a reproducing MR.
It comprises a composite head in which a head and a recording induction head are integrally formed.

That is, by controlling the direction and amount of energization to the voice coil motor 13, the actuator 1
2 and the load arm 11 oscillate in a plane parallel to the magnetic disk 10 with the oscillating speed and angle controlled.
Due to this swinging motion, the head 15 supported by the tip of the load arm 11 moves on the recording surface of the magnetic disk 10 in the radial direction of the magnetic disk 10, for example, concentrically on the recording surface of the magnetic disk 10. Performs a movement (seek operation) between a plurality of tracks arranged in the, and an operation of following a specific track.

The voice coil motor 13 and the spindle 14
, The operation of recording / reproducing data to / from the magnetic disk 10 via the head 15, and the data transfer to / from a higher-level device (not shown) are controlled by the control unit 16.

That is, the control unit 16 provides an interface control unit 16-6 for controlling the transmission and reception of data and commands to and from a higher-level device, gives a command to the servo system 16-2 according to a head positioning command, and controls the servo system 16- The servo control unit 16-1 receives the logical information from the host 2 and drives the R / W system to perform data read / write via the head 15 according to the data read / write command from the host device. And a status control unit 16-5 for generating a status of the magnetic disk device and transmitting it in response to a command from a higher-level device.

In this embodiment, a plurality of data tracks are arranged concentrically on the recording surface of the magnetic disk 10, and each data track has a servo information area between data areas (for example, data sectors). Are distributed in the circumferential direction. The servo control unit 16-1 and the servo system 16-2 of the control unit 16 control the head 15, the R /
By performing servo control as described below based on information read from each servo information area via the W system 16-4, the head 15 is positioned at a target position instructed by the host device, and data is recorded or reproduced. Perform the operation.

The servo control unit 16-1 of the control unit 16 according to the present embodiment, while writing data to a specific data track by the method shown in FIG.
5 determines that the track deviates from the track, generates a write fault signal and gives it to the R / W control section 16-3, and the R / W control section 16-3 inhibits the head 15 from writing data. Has a function of preventing data in another data track from being destroyed by erroneous writing.

FIG. 1 shows an example of the format of one servo information area according to the present embodiment, which is arranged in the circumferential direction of each of a plurality of data tracks on the magnetic disk 10.

In the example shown in FIG. 1, both the position detection and the speed detection are phase detection patterns. However, the present invention is not limited to the phase detection, and an example of the amplitude detection pattern will be described later. The configuration of FIG. 1 will be described. It comprises a pull-in area A on which a pattern of a single frequency is recorded, a track identification area B for providing sector information and track information, and a position signal / speed detection area C for obtaining position information and speed information in a track.

The position signal / speed detection area C includes a pair of patterns C-1 and C formed so as to have a predetermined azimuth angle of the same phase with respect to the circumferential direction of the data track.
-3 (velocity detection pattern area) and an opposite-phase pattern C-2 (position detection pattern area) interposed therebetween.

In the area C, the patterns C-1 and C-3 are in phase, and the area C-2 of the opposite phase is interrupted. The position information is detected from the phase difference between C1 and C-1 or C-3 (the detection area can be increased by combining C-1 and C-3 to improve the detection accuracy). As a phase position information detecting method, a digital detecting method as disclosed in JP-A-6-231552 is known.

In this embodiment, the magnetic disk 10
As shown in FIG. 2, the speed detection of the head 15 in the radial direction of the data track (denoted as a phase difference Δ)
It can be realized by observing the phase difference between the -1 part and the C-3 part. That is, in the case where there is no velocity in the radial direction (head locus 2), C-1 and C-3 are in-phase patterns and therefore C-
1 and C-3, there is no phase difference, but when there is a velocity in the radial direction (head locus 1), a phase difference Δ occurs. The phase detection may be considered in the same manner as the above-described position detection. However, in order to directly detect the phase difference for speed detection, the phases of C-1 and C-3 are shifted by π (rad) (180 degrees) in a pattern. ,
Instead of calculating the phases of C-1 and C-3 separately, C
If the -1 and C-3 regions are a series of calculation regions and the calculation is performed collectively, the calculation result indicates the phase difference, so that the calculation process can be simplified and the speed detection algorithm can be made more efficient. It can be realized.

In addition to using the pair of patterns,
In the case where there is a speed (head trajectory 1) as can be seen from the pattern (C-1) in FIG. 2, the frequency changes according to the speed compared to (head trajectory 2). It changes by ΔT.) Although the speed can be detected by focusing on this frequency change, consideration must be given to rotation fluctuations and the like, and synchronization detection using a PLL (phase lock loop) or the like is required. The pair of patterns C-
1, the detection at C-3 is advantageous in that if the distance between them is increased, the sensitivity is increased and there is no need for synchronous detection.

It is known that in a magnetic disk drive using a magnetoresistive head as a reproducing system of the head 15, a non-linearity appears in the position signal due to the sensitivity distribution in the radial direction of the head 15. In FIG. 1, in order to secure the linearity of the speed detection, the patterns C-1 and C-3 having azimuth are formed as continuous patterns. In a continuous pattern, there is no pattern change due to the position, so that there is no nonlinearity in the phase difference.
In order to record the continuous patterns for C-1 and C-3, the continuous patterns for C-1 and C-3 are previously recorded by heads having different moving directions as shown in FIG. When the magnetic disk 10 recorded on a part (recorded area 31 and unrecorded area 32) or the entire surface is incorporated into a magnetic disk device and a servo pattern is recorded on the magnetic disk device after assembly, the pattern shown in FIG. Retraction area A of
The track identification area B and the position signal area C-2 are overwritten and recorded. That is, this is realized by leaving a part of the pattern recorded in advance.

Many patterns are conceivable other than the pattern of FIG. 1 described above. Some cases are shown in FIGS.

FIG. 4 shows a pattern C-
1, C-3 are recorded discontinuously in the radial direction by the conventional method in the same manner as the reversed-phase pattern C-2, and there is no feature as a pattern, but the patterns C-1 and C-3 are used. This is different from the conventional device in that speed detection is performed by using the conventional method.

FIG. 5 shows that the position is detected by the pattern C-100.
Is a conventional amplitude detection using a phase pattern C-4 and a phase pattern C-5 for speed detection.

FIG. 6 shows an amplitude detection type for both the position and the speed.
(C-6) amplitude-(C-7) amplitude, or (C-8)
Amplitude-(C-9) Amplitude is used to detect a position change, and ｛(C-
6) Amplitude-(C-7) Amplitude｝ and ｛(C-10) Amplitude-
(C-11) The speed is detected from the difference in the amplitude｝. In this case, the head position can be detected only in the range near the track shown in the figure.

FIG. 7 is a diagram in which the pull-in area A-1 is also used as a phase reference pattern for speed detection, and the speed is detected by the phase difference between the pull-in area A-1 and the phase pattern C-12. The position is the amplitude detection by the pattern C-200. The detection sensitivity is improved in that the detection interval can be set wider than in the case of C-1 and C-3 in FIG. Thus, many patterns, arrangements, and the like are conceivable.

The speed detection in each servo information area has been described above. Next, an embodiment of a write fault signal using the speed detection will be described.

The write fault signal is a signal for stopping the recording operation when it is considered that the head position is largely shifted during the recording operation. In a magnetic disk drive of a sector servo system in which servo information only exists intermittently, prediction accuracy is poor if only a position signal obtained from each servo information is used. Therefore, for safety, the write fault signal is slightly shifted (position error signal). ), Which has been a factor in lowering the yield of the magnetic disk drive in the inspection process.

FIG. 8 is a conceptual diagram of a write fault signal generation using speed and position information in each servo information area according to the present invention. In a certain sector (t = 0), there is a displacement of Xo, and in the next sector (t = TT: sample period),
It is assumed that a position shift of 1 occurs. X1 <Xf (Xf:
Reference position deviation amount for write fault) but speed is V
Assuming that at 1, at t = 2T, (X1 + V1
× T) is predicted.

Therefore, X1 + V1 × T <Xf is set as a write fault determination condition. In the case of FIG. 8, recording is prohibited (write fault) at t = T, and data destruction of an adjacent track can be prevented. As can be seen from this example, it can be seen that the determination can be made more safely by using the result of speed detection without delay (speed detection within the same sector). Note that also in this case, t = T1 to T2
Is a prediction, and the prediction may vary depending on the situation of the external force. Therefore, the above determination formula should be considered as an example.

Next, FIG. 9 shows an example of a configuration for introducing speed to the servo system 16-2, for compressing force disturbance and for compressing mechanical system resonance. FIG. 9A shows a feedback system in the servo system 16-2 in the control unit 16 of the magnetic disk drive of the present embodiment, which is characterized in that the speed term is fed back. Y indicates a track on the magnetic disk 10, and X indicates a head position. The position error signal demodulator converts the position error amount between Y and X into a voltage. G (z)
Is a digital filter, which is composed of a position feedback system and a speed minor loop system. As will be described later, the speed signal demodulator 16-2a separates the position and the detected speed into bands, and detects a highly accurate speed. DA converts digital signals into analog voltages.
P. A is a power amplifier that converts a voltage into a current and drives a voice coil motor (VCM) 13. kf is VCM13
, And M indicates the working mass. S is a Laplace operator and 1 / S indicates integration. Therefore, VCM1
The acceleration of the mass M is generated by the current 3 and the speed is obtained by integrating the acceleration, and the position X is obtained by integrating the speed.

Here, the speed signal demodulator 16-2a, which is a feature of the present configuration, will be described in detail with reference to FIG.
The speed detected at the same time as the position (the speed detection described in FIG. 1 or the like; Vs) can be regarded as having high sensitivity in a high frequency region and almost no detection delay. On the other hand, the speed at which the differential such as the backward difference of the position is calculated by calculation has high accuracy in the low frequency range and the delay can be ignored. However, in the high frequency range, the delay is large and this is inconvenient in configuring the servo system 16-2. . The speed signal demodulator 16-2a passes the backward difference of the position through a low-pass filter (LPF), and the speed Vs described in the present embodiment is:
After passing through a high-pass filter (HPF), addition was performed.
In FIG. 9B, 1 / z indicates a value one sample before. a is a contact frequency (for example, a = 2 × π × 1000). T
Is the sample period. The synthesized speed indicates a speed with no delay over the entire servo band. Therefore, by feeding back the speed, the force disturbance acting on the actuator 12 and the compression of the mechanism resonance can be reduced. Note that HPF, L
The calculation of PF should be considered as an example. As the speed feedback, a first-order system of the speed term and the differential term such as (c1 + c2 × (1-1 / z) / T) V (where c1 and c2 are constants) is preferable. Speed feedback is known to be effective against force disturbances in the low-frequency region.However, speed detection based on the difference in position causes a phase delay at high frequencies, and the adverse effects of force disturbance suppression appear in the high-frequency region. Was. Since the speed detection described in the present invention does not cause a delay even in a high frequency range,
Only the force disturbance in the low frequency region can be suppressed.

By feeding back the acceleration, the mechanism resonance can be suppressed. Mechanism resonance is high frequency,
Also in this case, when detecting the acceleration from the position, the delay is similarly large, and it is difficult to realize. It was found that when calculating the acceleration from the speed difference without delay, the delay was small and the suppression was possible to some extent.

In addition to the servo system described above, an observer whose position and speed are to be compared can be constructed.

As described above, in the magnetic disk drive of this embodiment, in each of the plurality of servo information discretely arranged in the circumferential direction on the track of the magnetic disk 10, the speed information is simultaneously transmitted with the position signal. I tried to get
There is no delay such as speed information obtained from a difference between a plurality of position signals (servo information) unlike the related art, and the reliability of the write fault signal is improved. In other words, it is not necessary to set the head position shift amount, which is a reference for generating a write fault signal, more strictly than necessary, and the number of magnetic disk devices that fail in the inspection process is reduced, and the yield is improved.

Further, also in the servo system, force disturbance and mechanical system resonance can be compressed, so that the servo system can be improved and the head positioning accuracy can be improved.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments and can be variously modified without departing from the gist thereof. Needless to say, there is.

[0044]

According to the magnetic disk drive of the present invention, it is possible to improve the servo system and improve the accuracy of the write fault signal.

Further, an effect is obtained that the detection algorithm for speed detection can be made more efficient.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a configuration of a servo information area on a magnetic disk in a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing an example of an operation of the magnetic disk device according to one embodiment of the present invention.

FIG. 3 is a conceptual diagram for explaining an example of a method for forming servo information in a magnetic disk device according to an embodiment of the present invention.

FIG. 4 is a conceptual diagram showing a modification of the configuration of the servo information area on the magnetic disk in the magnetic disk device according to one embodiment of the present invention.

FIG. 5 is a conceptual diagram showing a modification of the configuration of the servo information area on the magnetic disk in the magnetic disk device according to one embodiment of the present invention.

FIG. 6 is a conceptual diagram showing a modification of the configuration of the servo information area on the magnetic disk in the magnetic disk device according to one embodiment of the present invention.

FIG. 7 is a conceptual diagram showing a modification of the configuration of the servo information area on the magnetic disk in the magnetic disk device according to one embodiment of the present invention.

FIG. 8 is a diagram showing an example of a method of generating a write fault signal in the magnetic disk device according to one embodiment of the present invention.

FIGS. 9A and 9B are conceptual diagrams showing an example of the configuration of a servo system in a magnetic disk drive according to an embodiment of the present invention.

FIG. 10 is a partially cutaway perspective view showing an example of a configuration of a magnetic disk drive according to an embodiment of the present invention.

[Explanation of symbols]

1, 2 ... head locus, 10 ... magnetic disk, 11 ... load arm, 12 ... actuator, 12a ... pivot shaft, 13 ... voice coil motor (VCM), 14 ... spindle, 15 ... head, 16 ... controller, 16- DESCRIPTION OF SYMBOLS 1 ... Servo control part, 16-2 ... Servo system, 16-3 ... R / W control part, 16-4 ... R / W system, 16-5 ... Status control part, 16-6 ... Interface control part, 16- 2a ...
Speed signal demodulator, 31: recorded area, 32: unrecorded area, A: pull-in area, A-1: pull-in area, B: track identification area, C: position signal / speed detection area.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akagi Kyo 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo F-term in Hitachi, Ltd. Central Research Laboratory 5D096 AA03 BB01 CC01 DD02 EE03 GG01 HH07 HH09 KK12 5D109 KA17 KB04 KD12 KD18 KD23

Claims (3)

[Claims] 1. A magnetic disk, comprising: a head for performing an operation of recording and reproducing information on and from a data track set on the magnetic disk; and a positioning mechanism for performing an operation of positioning the head with respect to the magnetic disk. A sector servo type magnetic disk device in which a servo information area is intermittently arranged on a data track and the head is positioned on any of the data tracks based on servo information read from the servo information area, A magnetic disk drive wherein a speed signal is generated from a servo information area together with a position signal relating to the head, and a write fault signal for inhibiting the recording operation by the head is generated using both the position signal and the speed signal. . 2. A magnetic disk, comprising: a head for performing an information recording operation and a reproducing operation on a data track set on the magnetic disk; and a positioning mechanism for performing a positioning operation of the head with respect to the magnetic disk. A sector servo type magnetic disk device in which a servo information area is intermittently arranged on a data track and the head is positioned on any of the data tracks based on servo information read from the servo information area, A velocity signal is generated together with a position signal from the servo information area, and a signal obtained by differentiating the position signal and a velocity signal are separated into bands to form a new composite velocity signal, which is synthesized. A magnetic disk drive characterized by comprising a servo system. 3. The magnetic disk drive according to claim 1, wherein the servo information area has a pair of speed detection pattern areas that partially use or include a position detection pattern area. In the first configuration, at least a part of the speed detection pattern area includes a second pattern that is already recorded before the magnetic disk is incorporated in the magnetic disk device.
The speed detection pattern region is composed of a pair of phase patterns, speed detection is performed by detecting a phase difference between the pair of phase patterns, and the phase difference between the pair of phase patterns is 180 degrees. A magnetic disk drive comprising any one of a third configuration and a third configuration.