JPH04255975A - Method for correcting off-tracking of magnetic disk device - Google Patents

Abstract

PURPOSE:To accurately correct off-tracking when a shock or a vibration is applied to a magnetic disk device while reading servo information DSD on a data face. CONSTITUTION:Plural magnetic disks 2 having servo faces 2a and data faces 2b, plural magnetic heads 3, a head positioning mechanism 5 which positions plural magnetic heads 3 to a desired track, and a control part 6 which controls the head positioning mechanism 5 are provided. And, in the magnetic disk device in which, by the control part 6, the servo information on the data face is read out, the off-track correcting data is calculated and updated, the head positioning is controlled by means of the servo information on the servo face and the off-track correcting data, when the shock or vibration applied to the magnetic disk device is detected by the control part 6 while reading the servo information on the data face, the update of the off-track correcting data by means of the read-out servo information is not executed.

Description

[Detailed description of the invention]

(Table of Contents) Industrial Application Fields Prior Art (Fig. 5) Problems to be Solved by the Invention (Fig. 6) Means for Solving the Problems (Fig. 1) Working Example (a) One Example Explanation (FIGS. 2 to 4) (b) Explanation of other embodiments Effects of the invention

0002

[Industrial Application Field] The present invention obtains off-track correction data from servo information on the data surface of a magnetic disk.
The present invention relates to an off-track correction method for a magnetic disk device that corrects track positioning using off-track correction data.

[0003] In recent years, with the demand for larger capacity computer systems, there has been a demand for higher density track pitches in magnetic disk drives.

[0004] As the track pitch becomes denser as described above, minute track deviations between the same cylinders due to differences in the amount of expansion and contraction of each magnetic disk, spindle wobbling, etc. cannot be ignored, and off-track occurs.

[0005] Therefore, such an off-track correction technique is required.

[0006]

2. Description of the Related Art FIG. 5 is an explanatory diagram of the prior art.

In the figure, 1 is a spindle, which serves as a rotating shaft, 2 is a magnetic disk, which is attached to the spindle 1 and rotates, and 3 is a magnetic head, which reads/writes data on the magnetic disk 2. something for lighting,
4 is an actuator that supports and drives the magnetic head 3; 5 is a voice coil motor (VCM) that drives the actuator 4;

In such a magnetic disk device, data surface servo information DSD is written not only on the servo surface of the magnetic disk 2 but also on a specific area on the data surface, and the magnetic head 3 writes this information at the time of initial seek or automatic adjustment. The data surface servo information DSD is read, the amount of off-track is calculated, and stored in a memory or the like, and when the head is positioned, correction is made using this amount of off-track in addition to the servo information of the servo surface.

At this time, since the off-track amount changes over time, the magnetic head 3 is
This data surface servo information DSD was read in, the off-track amount was calculated, and the off-track amount was updated in the memory.

0010

6 is a diagram illustrating problems in the prior art.

[0011] Incidentally, shocks and vibrations may be applied to the magnetic disk device from the outside.

For example, when active maintenance is performed, shocks and vibrations are applied to the operating magnetic disk device when an adjacent magnetic disk device is inserted and removed for replacement.

If such a shock or vibration occurs while reading the data surface servo information DSD, as shown in FIG. 6(B)
As shown in , the position signal based on the servo information on the servo surface vibrates, and the locus of the magnetic head 3 of the data surface servo information DSD also vibrates, so the read signal of the data surface servo information DSD fluctuates, causing off-track correction. The signal is calculated incorrectly.

[0014] When the off-track amount is updated in this way,
In the subsequent off-track correction, a problem arises in that the magnetic head cannot be correctly positioned at the center of the track, and the output of the magnetic head 3 becomes unstable during reading, causing read errors, and during writing, off-track errors occur. It was the cause.

Moreover, this erroneous off-track correction amount is not corrected until the next automatic adjustment, and there is a problem that the error state continues.

Therefore, the present invention provides data surface servo information D
An object of the present invention is to provide an off-track correction method for a magnetic disk device that can perform accurate off-track correction even if shock or vibration is applied to the magnetic disk device while reading an SD.

[0017]

[Means for Solving the Problems] FIG. 1 is a diagram showing the principle of the present invention.

Claim 1 of the present invention provides a plurality of magnetic disks 2 having a servo surface 2a and a data surface 2b, a plurality of magnetic heads 3, and a head for positioning the plurality of magnetic heads 3 on desired tracks. It has a positioning mechanism 5 and a control section 6 that controls the head positioning mechanism 5, and the control section 6 reads the servo information of the data surface, calculates and updates off-track correction data, and updates the servo information of the servo surface. In a magnetic disk device that performs head positioning control using servo information and the off-track correction data, the control unit 6 detects a case where shock or vibration is applied to the magnetic disk device while reading the servo information on the data surface. If this is detected, the off-track correction data is not updated using the read servo information.

[0019] Claim 2 of the present invention provides the following in claim 1:
After detecting the impact or vibration, the control unit 6
The method is characterized in that the servo information on the data surface is read out again.

According to a third aspect of the present invention, in the first and second aspects, the control section 6 compares the amplitude of the servo information on the servo surface 2a with a predetermined tolerance value, and controls the magnetic disk drive. The device is characterized by detecting that an impact or vibration is applied to the device.

According to a fourth aspect of the present invention, in the first and second aspects, the control unit 6 compares the off-track correction data based on the read servo information with the previous off-track correction data, and It is characterized by detecting that an impact or vibration is applied to a magnetic disk device.

[0022]

[Operation] According to claim 1 of the present invention, when it is detected that an impact or vibration is applied to the magnetic disk device while reading the servo information on the data surface, off-track correction data based on the read servo information is Since it does not perform updates,
Off-track correction due to incorrect off-track correction data caused by servo information read during shock or vibration can be prevented, and read errors etc. can be reduced.

According to claim 2 of the present invention, the servo information on the data surface is re-read after detecting an impact or vibration, so it is possible to immediately update the off-track correction data in response to a temporary impact or the like. Become.

In claim 3 of the present invention, the amplitude of the servo information on the servo surface 2a is compared with a predetermined tolerance value to detect that an impact or vibration is applied to the magnetic disk device, so that off-track updating is performed. It is possible to easily and accurately detect shocks that affect the environment.

According to the fourth aspect of the present invention, the off-track correction data based on the read servo information is compared with the previous off-track correction data to detect that an impact or vibration has been applied to the magnetic disk drive. Impacts that affect off-track updates can be easily and accurately detected.

[0026]

Embodiment (a) Description of an Embodiment FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a block diagram of a control section in FIG.

In the figure, the same parts as those shown in FIGS. 1 and 5 are indicated by the same symbols, and 3a is a servo head, which is provided corresponding to the servo surface 2a of the magnetic disk 2. 3b for reading servo information on servo surface 2a;
is a data head, and the data surface 2b of the magnetic disk 2
It is provided to read/write data surface 2b and read servo information from data surface 2b.

60 is a position demodulation circuit that demodulates a position signal from servo information from the servo head 3a; 61 is a data surface servo demodulation circuit that demodulates data surface servo information from the data head 3b; Reference numeral 62 denotes an impact detection circuit, which detects an impact on the magnetic disk drive from a position signal, which will be described later with reference to FIG. 64 is a microprocessor (MPU) that executes off-track amount measurement processing, off-track correction processing, etc.

65 is a memory which stores data and programs necessary for the operation of the MPU 64 as well as off-track correction data; 66 is a timer;
67 is a D/A (digital/analog) converter that converts the off-track correction data from the MPU 64 into an analog quantity; 68 is a position error detection circuit that detects an error from a position signal and outputs an off-track amount; 69 is a power amplifier;
It converts the output of the position error detection circuit 68 into a current of the coil of the VCM 5.

The impact detection circuit 62, as shown in FIG.
A first comparator 62 that subtracts a positive first reference value from the position signal and issues a low-level impact detection output when the subtraction result is positive (position signal>first reference value).
subtract the position signal from a and a negative second reference value,
When the subtraction result is positive (second reference value > position signal), the second comparator 62b that issues a low-level impact detection output and the outputs of both comparators 62a and 62b are ANDed to generate an impact detection signal. Generated AND gate 62
c, and voltage dividing resistors R1 and R for setting the first reference value.
2, and voltage dividing resistors R3 and R for setting the second reference value.
4.

FIG. 4 is a flowchart of an off-track measurement process according to an embodiment of the present invention.

After clearing the impact flag in the memory 65, the MPU 64 seeks to the cylinder in which the data surface servo information DSD is written in the process of initial seek or automatic adjustment seek due to timeout of the timer 66, and then performs data surface servo control. Demodulation circuit 61, A/D converter 63
Start reading the data surface servo information DSD via the .

(2) While reading this data plane servo information DSD, the MPU 64 monitors the impact detection signal of the AND gate 62c of the impact detection circuit 62.

[0034] ■ The MPU 64 stores data surface servo information DS.
While reading D, if there is no external impact, the amplitude of the position signal is small, and no impact detection signal is generated, and the servo information is successfully read, as shown in Figure 6 (A). New off-track correction data is calculated from the read servo information, and the off-track correction data in the memory 65 is updated.

After that, the MPU 64 sets the normal time until the next automatic adjustment seek in the timer 66, starts the timer 66, and ends the initial seek or automatic adjustment seek process.

■Meanwhile, while reading the data surface servo information DSD in step ■, an external shock is applied, causing the
As shown in B), when the position signal has a large amplitude and an impact detection signal is generated, the MPU 64 outputs the memory 65.
Set the impact flag and stop reading the data surface servo information DSD.

When this impact flag is set, the subsequent off-track correction data calculation processing is not executed, and the timer 66 is set to a shorter time than in the normal case and activated. Therefore, the process times out in a shorter time than in the normal case, rereads the data surface servo information, and repeats this sequence until the process ends normally.

In this way, the data surface servo information DS
If an external shock is applied while reading D, reading of the data surface servo information is stopped and off-track correction data in the memory 65 is not updated.

Furthermore, since the impact is detected by monitoring the position signal based on the servo information on the servo surface, it is possible to detect the impact that affects the reading of the data surface servo information, and moreover, it can be detected easily.

(b) Description of other embodiments In addition to the embodiments described above, the present invention can be modified as follows.

■ Although the impact detection circuit 62 is configured with hardware, the MPU 64 calculates the difference between the off-track correction amount calculated from the data surface servo information and the previous off-track correction amount, and if the difference is constant. If the value exceeds the value, it may be determined that an external impact has been applied, and the off-track correction data may not be updated.

[0042] In this case, all data surface servo information is read regardless of external impact.

[0043] Also, impact detection may be performed using a well-known acceleration sensor or the like.

[0044] When an external impact is detected when reading the data surface servo information, the data surface servo information may be reread immediately without opening for a certain period of time.

[0045] The data surface servo information area is set as one round of the track so that rotational vibration of the magnetic disk can be corrected, but it may also be a sector area.

The present invention has been explained above using examples, but
Various modifications are possible within the scope of the present invention, and these are not excluded from the scope of the present invention.

[0047]

[Effects of the Invention] As explained above, according to the present invention,
It has the following effects.

■ Since the off-track correction data is not updated by detecting the impact or vibration applied to the magnetic disk drive, incorrect off-track correction data may be generated due to data surface servo information that changes due to impact or vibration. This prevents errors during off-track correction.

(2) Since the data is not updated with incorrect off-track correction data, it is possible to prevent the error state from continuing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a block diagram of a control unit according to an embodiment of the present invention.

FIG. 4 is a flow diagram of an off-track measurement process according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of the prior art.

FIG. 6 is a diagram illustrating problems in the prior art.

[Explanation of symbols]

2 Magnetic disk 2a Servo surface 2b Data side 3 Magnetic head 5 Head positioning mechanism 6 Control section

Claims (4)

[Claims] [Claim 1] Servo surface (2a) and data surface (2b)
a plurality of magnetic disks (2), a plurality of magnetic heads (3), and a head positioning mechanism (5) for positioning the plurality of magnetic heads (3) on desired tracks;
a control unit (6) that controls the head positioning mechanism (5), the control unit (6) reads servo information on the data surface, calculates and updates off-track correction data, and controls the servo surface. In a magnetic disk drive that performs head positioning control using the servo information on the data surface and the off-track correction data, the control unit (6) applies shock or vibration to the magnetic disk drive while reading the servo information on the data surface. 1. An off-track correction method for a magnetic disk drive, characterized in that when it is detected that the servo information is applied, off-track correction data is not updated using the read servo information. 2. Off-track correction for a magnetic disk device according to claim 1, wherein the control unit (6) executes re-reading of servo information on the data surface after detecting the shock or vibration. Method. 3. The control unit (6) is configured to control the servo surface (
3. The magnetic disk device according to claim 1 and claim 2, wherein the amplitude of the servo information of 2a) is compared with a predetermined tolerance value to detect that an impact or vibration is applied to the magnetic disk device. off-track correction method. 4. The control unit (6) compares the off-track correction data based on the read servo information with the previous off-track correction data, and determines whether an impact or vibration has been applied to the magnetic disk device. 3. The off-track correction method for a magnetic disk device according to claim 1, further comprising the step of: detecting.