JPH02235258A - Method for measuring whirling off-track value of magnetic disk medium - Google Patents

Abstract

PURPOSE:To eliminate the need for reading work in an off-track measuring process and to attain highly accurate, quantitative and automatic measurement by finding out a change in the off-track value from a change value in each sector of the off-track value. CONSTITUTION:An output voltage is dropped in accordance with the off-track of a magnetic head from the position C of a track and an error generating ratio is increased. Thereby, the track C exists in the intermediate position between an foreword offset margin with a circular mark and a reverse offset margin with a triangular mark. The shown graph is obtained by plotting the position of the track C in each sector and the dynamic change of the off-track value can be read out. The peak point DELTAC on the graph shows the maximum off-track value due to the whirling of a magnetic disk medium, an eccentric value of the magnetic disk medium can be obtained from the maximum off-track value and the eccentric direction can be detected from the position of the track including the peak value. Consequently, the reading work in the off-track measuring process can be omitted and highly accurate, quatitative and automatic measurement can be attained.

Description

[Detailed Description of the Invention] [Summary] Combu. −? Regarding the method of measuring the amount of off-track of the magnetic head due to whirling of the magnetic disk medium in a magnetic disk device used as a file device of a data system, it is possible to improve the Aiming at realizing a measurement method that is accurate, quantitative, and capable of automatic measurement, in a magnetic disk device, one track of a magnetic disk medium is divided into n sectors and formatted. #J After applying a predetermined environmental stress to the magnetic disk device, measure the offset margin of the magnetic head in the forward direction and reverse direction for each sector, find the intermediate value between the margins, and calculate the intermediate value between the magnetic disks. The amount of off-track of the magnetic head caused by deviation of the center of rotation of the medium is taken as the amount of off-track of the magnetic head, and the change in the amount of off-track is determined from the amount of change in the amount of off-track for each sector.

[Industrial application field]

The present invention relates to a method for measuring the off-track amount of a magnetic head due to whirling of a magnetic disk medium in a magnetic disk device used as a file device of a computer system. [Overview of Mechanism of Magnetic Disk Device] FIG. 5 is a perspective view illustrating an overview of the mechanism of the magnetic disk device. In the magnetic disk device, a plurality of magnetic disk media 1 are mounted on a spindle 2 and rotated at high speed by a motor 3. Each magnetic disk medium 1 is provided with a magnetic head 4 facing the surface thereof, and is floated by the wind force generated by the high speed rotation of the magnetic disk medium 1. You can also read/write information.
te) is performed by moving the magnetic head 4 to a predetermined track position using the positioning mechanism 6.

The track position is determined by using one of the magnetic disk media l as a servo disk, recording servo signals on the tracks of the servo disk, and reading the servo signals.

That is, the magnetic heads 4 disposed on each surface of the magnetic disk medium 1 are driven simultaneously by the positioning mechanism 6.
The tracks on each disk are aligned with the tracks on the servo disk as a reference.

Therefore, when the magnetic disk drive is in use, the occurrence of a change in the relative position between the disks of the magnetic disk medium l becomes a factor that fundamentally destroys the reliability of the magnetic disk drive.

In other words, the magnetic head 4 may not be positioned on a predetermined track, resulting in off-track, resulting in an error in read data, or in extreme cases, it may become impossible to read recorded data, or data may be written on an adjacent track. This is because the data will be destroyed. Additionally, with the miniaturization and increased storage capacity of magnetic disk devices, the recording density on magnetic disk media has increased.
The existence of off-track is an important factor that determines the reliability of magnetic disk devices. The present invention relates to a method for measuring this off-track. [Prior Art] (1) Wandering and off-track FIG. 6 is a plan view illustrating whirling off-track of a magnetic disk medium. Wandering refers to rotational wobbling caused by the magnetic disk medium rotating around a point other than the normal center point 7 of the magnetic disk medium, for example, an eccentric center point 8.

In other words, the track on the magnetic disk medium is a perfect circle,
If the center of rotation coincides with the center of the perfect circle, the track always rotates on the same track as when it is at rest, even during rotation. However, if the center of rotation is eccentric, each point on the track will rotate with its own unique radius of rotation, and when viewed from the magnetic head, it will appear as if the track is vibrating. . This is whirling off-track. In FIG. 6, the track 10 in the normal state is the position of the track when the normal center point 7 is the center of rotation, but the track 12 in the eccentric state is the position of the track when the center of rotation is about the eccentric center point 8. This is the position of the track in case. therefore,
When viewed from the magnetic head 4, off-track ΔC occurs with respect to the track 12 during eccentricity. FIG. 7 is a diagram illustrating the relationship between the inclination of the rotation axis of the magnetic disk medium and the off-track of the magnetic head, in which (a) is a side view of the magnetic disk medium, magnetic head, and positioning mechanism, (b) and (c). ) is a diagram explaining the relationship between each magnetic head and the amount of off-track. Figure (b). (c) shows the off-track amount when the rotating shaft 13 is tilted to the left in the figure.

(b) shows the case where the disk D1 of the magnetic disk medium 1 is a servo disk, and the lower surface of the disk D1 is the servo surface in the figure. Therefore, of the magnetic heads 4, the off-track of the head Hla that traces the servo track is 0 (zero), and the higher the magnetic head is located in the diagram, the larger the off-track amount. (c) shows the case where the disk D3 of the magnetic disk medium 1 is a servo disk, and the lower surface of the disk D3 is the servo surface in the figure. Therefore, among the magnetic heads 4, the off-track of the head 83a that traces the servo track is 0 (zero), and the off-track amount of other magnetic heads increases as the distance from the head H3a increases. FIG. 8 is a diagram illustrating off-track due to eccentricity of a magnetic disk medium. This figure explains a case where eccentricity occurs in the disk D3. (a) shows the case where the disk D1 is a servo disk, and the heads H3a. Off-track occurs only in H3b. (b) shows the case where the disk D3 is a servo disk, and off-track occurs in all magnetic heads other than heads H3a and H3b of the magnetic head 4.

(2) Off-track measurement method Conventionally, this off-track measurement was performed by an operator visually reading the observed waveform on an oscilloscope. Figure 9 is a diagram explaining the method of measuring the whirling off-track amount using the conventional analog method, in which Ca) is the signal pattern of the measurement track, and (b) is the output voltage waveform of the magnetic head when there is no off-track. , (c) is the output voltage waveform of the magnetic head when there is off-track, (d) is (
The amount of off-track converted from the difference in output voltage in c) is explained. Figures (a) and (b). (c). In (d), the horizontal axis in (a) represents the track distance,
(b). (c). The horizontal axis in (d) represents time. However, magnetic de... Since the disk medium rotates at a constant cycle, each position of the measurement track as seen from the magnetic head and the time axis of the output voltage of the magnetic head have a correlation that repeats at a constant cycle. Therefore, in Figure 9, these are treated as the same. The measurement procedure will be explained below.

Procedure ■... Record the measurement signal on the measurement track. Signal patterns A and B having the same frequency and the same level are written on the measurement track by moving the magnetic heads off-track to positions in opposite directions with a certain amount of offset from the on-track position. Figure (a) shows this.

Procedure ■...Apply environmental stress such as temperature stress to the magnetic disk drive.

Magnetic disk drives expand and contract due to temperature changes, resulting in irreversible misalignment. Procedure ■: Observe the output voltage waveform of the magnetic head with an oscilloscope. The measurement recording signals on the magnetic disk medium are recorded at positions opposite to each other with a certain amount of offset from the on-track position.

Therefore, if there is no off-track in the magnetic head, the output voltages of the magnetic head will match between the recording signal A part and the recording signal B part in the diagram (a).

However, if off-track exists in the magnetic head,
The output voltage of the recording signal in the direction of the position where off-track occurs increases, and the output voltage of the recording signal in the opposite position decreases.

(b) shows the output voltage of the magnetic head when there is no off-track, and the output voltage Va of the recording signal A portion and the output voltage vb of the recording signal B portion are Va = Vb.

In addition, FIG. 3(c) shows a case where off-track occurs on the recording signal A side, and the output voltage Vaa of the recording signal A portion and the output voltage vbb of the recording signal B portion satisfy Vaa>Vbb. Step ■... Convert the amount of off-track from the output voltage of the magnetic head. Figure (d) shows the change in off-track ΔC of the magnetic head calculated from the difference in output voltage shown in Figure (c).

The off-track amount of the magnetic head was measured as described above. [Problems to be Solved by the Invention] However, the above method requires an operator to observe the output voltage of the magnetic head using an oscilloscope. In other words, it is measured by visual reading. Therefore, there is a problem in that reading errors occur and it is not possible to measure the off-track amount due to whirling of the magnetic disk medium with high accuracy and quantitatively.

The technical problem of the present invention is to solve the above-mentioned problems in off-track measurement of whirling magnetic disk media, and to eliminate the need for operators to perform reading operations during the off-track measurement process, thereby achieving highly accurate and quantitative measurement. The object of the present invention is to realize a measuring method that is capable of automatic measurement.

[Means to solve the problem]

FIG. 1 is a diagram explaining the basic principle of the present invention, in which (a) is a flowchart of the measurement procedure, and (b) is a change in the off-track amount obtained from the measurement results.

The present invention is a method for measuring the amount of whirling off-track using the following procedure. (2) Divide and format one track of the magnetic disk medium into n sectors.

■Apply a predetermined environmental stress to the magnetic disk drive as a measurement condition. ■Measure the offset margin of the magnetic head in the forward direction where the cylinder value increases and in the reverse direction where the cylinder value decreases for each sector. (2) Determine the intermediate value between the forward offset margin and the reverse offset margin of each sector, and use the intermediate value as the amount of off-track of the magnetic head caused by deviation of the center of rotation of the magnetic disk medium.

■From the change in off-track amount for each sector in ■ above,
The dynamic change in the amount of whirling off-track caused by the deviation of the center of rotation of the magnetic disk medium due to the environmental stress mentioned in (2) above is determined. That's it. [Operation] The method of the present invention measures the offset margin of the magnetic head in the forward direction and the reverse direction for each sector,
The feature is that the intermediate value of the margin is taken as the off-rack amount. FIG. 2 is a diagram illustrating the principle of determining the track position from the reverse offset margin and forward offset margin, where the horizontal axis represents the position of the magnetic head and the vertical axis represents the read error rate.

As the magnetic head moves off-track from track position C, the output voltage decreases and the error rate increases.

Therefore, the offset value at a predetermined error rate Er when the magnetic head is offset in the forward direction where the cylinder value increases, and the offset value when the magnetic head is offset in the reverse direction where the cylinder value decreases.
The offset value at a predetermined error occurrence rate Er matches. That is, track C exists at an intermediate position between the forward offset margin marked Q and the reverse offset margin marked Δ.

FIG. 1(b) is a diagram in which the position of the track C is plotted for each sector, and dynamic changes in the amount of off-track can be read. Also, the peak point ΔC on the diagram indicates the maximum amount of off-track due to whirling of the magnetic disk medium, and from this value, the amount of eccentricity of the magnetic disk medium can be determined, and the track where the peak value exists can be determined. The direction of eccentricity can be determined from position 1.

〔Example〕

(1) Block diagram FIG. 3 is a block diagram of the embodiment.

The magnetic disk device 27 has a mechanical system consisting of a magnetic disk medium 1, a motor 3 that rotates the magnetic disk medium 1, a magnetic head 4, a positioning mechanism 6, etc., a motor drive section 20 that drives the motor 3, and a magnetic head 4. a read/write unit 19 that reads/writes data to the magnetic disk medium 1; a positioning control unit 17 that controls the positioning of the magnetic head 4; Control unit 18 that controls control unit 17
It consists of a control system consisting of: The magnetic disk device 27 as described above is connected to the test device 22 via the interface section 21. Test equipment 2
2 communicates with and controls the magnetic disk device 27 via a control signal 23, an address signal 24, a read/write signal 25, etc. The control unit 18 has a command to issue a command to the positioning control unit 17 to offset the magnetic head 4 by a predetermined amount from the track position, and the test device 22 sends an offset command via the interface unit 21. It is carried out by However, if the control unit 18 does not have an offset command, the offset signal (direct
connection to send an offset signal 26).

Further, the read/write signal 25 is transmitted to the read/write section 1
9 and the test device 22 via the interface unit 21, the test device 22 sends write data, the test device 22 receives read data, and also checks errors in the received data. Check for presence.

(2) Measurement FIG. 4 is a diagram explaining the embodiment, (a) is a flowchart of the basic measurement process, (b) is a flowchart of the offset/margin measurement process, (C) is how the track is divided into sectors, (d) shows how the off-track changes;
(e) is the eccentricity amount and eccentric position of the magnetic disk medium.

In this example, one track is divided into 16 sectors, formatted, and measured.

The measurement procedure is shown in FIG. 4(a) and will be explained step by step below.

Procedure ■ Divide and format one track into 16 sectors.

Incidentally, each sector is composed of an ID section 14 and a DATA section 15, as shown in FIG. 4(c).

Procedure ■ Apply temperature stress to the magnetic disk drive. (However, if you want to measure the amount of off-track caused by other factors, add the stress that causes it. For example, use vibration.) Procedure ■ Set the measurement sector number to O (zero).

Procedure ■ Measure the forward offset margin of the measurement sector. (The method for measuring the offset margin will be explained later.) Procedure ■ Measure the reverse offset margin of the measurement sector. Procedure ■ Add 1 to the measurement sector and repeat steps ■ and ■ until sector number 15.

That's it. The forward offset margin and reverse offset margin are now measured for each sector. Moreover, by defining the relationship between the offset command and the offset amount, the offset amount can be measured as a direct reading value. The offset margin measurement process is shown in Figure 4 (b).
). In this procedure, the magnetic head is offset to the maximum in advance, the measurement sector is read repeatedly and continuously, the offset amount is sequentially reduced a predetermined number of times until the position where no error occurs, and the offset amount at that time is set as the offset margin value. This is what we mean. The following is a step-by-step explanation. Procedure ■ Offset the magnetic head on the measurement track to the maximum in the forward direction (direction where the cylinder value increases) or reverse direction (direction where the cylinder value decreases).

Thousand order ■ Clear the read count counter that counts the number of reads (set it to 0). Procedure■ Read the device. That is, read the specified sector.

Procedure ■ If a reading error occurs, reduce the offset amount by a certain amount and restart the measurement from step ■.

If there is no read error, 1 is added to the read count counter.
Add and proceed to step ■. Step ■ If the number of readings has not reached the predetermined number, repeat from step ■. However, when the number of readings reaches a predetermined number, the measurement is ended using the offset value at that time as the offset margin.

That's all.

(3) Derivation of whirling off-track Figure 4(d) shows the whirling off-track amount determined from the forward offset margin and reverse offset margin measured for each sector. That is, for each sector, the forward offset
This is the intermediate value between the margin and the reverse offset margin. In the figure, C is the track position, sector number 3
The maximum off-track amount of 2 μm occurs in this case. Therefore, as shown in FIG. 4(e), there is an eccentric center 8 at a position 2μ flaw from the normal center point 7. Further, as shown in FIG. 4(d), when the off-track changes in a sinusoidal manner, this is the case when eccentricity occurs in the magnetic disk medium or when the axis of the spindle (rotation shaft) is bent. On the other hand, if the spindle (rotation axis) is tilted, each sector will have the same off-track amount.

〔Effect of the invention〕

As described above, according to the measuring method of the present invention, it is possible to measure the off-track amount of whirling of a magnetic disk medium using the intermediate value between the forward offset margin and the reverse offset margin of each sector of the magnetic disk medium. Therefore, there is no need for the operator to perform reading operations during the off-track measurement process, making it possible to measure the off-track amount with high precision and quantitatively, and at the same time, it is also possible to automate the turning off-track measurement. As a result, the amount of whirling off-track of the magnetic disk medium can be measured with high reliability, and at the same time, productivity in this measurement is dramatically improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the basic principle of the present invention. (a) is a flowchart of the measurement procedure, (b) is a change in off-track amount obtained from the measurement results, and FIG. 2 is a diagram showing the track position. FIG. 3 is a block diagram of the embodiment; FIG. 4 is a diagram explaining the embodiment; (a) is a flowchart of the basic measurement process; (b) is a diagram of the offset margin. Measurement processing flowchart, (C) shows how the track is divided into sectors, (d) shows how off-track changes, (
e) is a diagram illustrating the amount of eccentricity and eccentric position of the magnetic disk medium, FIG. 5 is a perspective view illustrating the outline of the mechanism of the magnetic disk device, and FIG. FIG. 7 is a plan view for explaining the relationship between the inclination of the rotation axis of the magnetic disk medium and the off-track of the magnetic head, and (a) is a side view of the magnetic disk medium, magnetic head, and positioning mechanism; b) and (c) are diagrams explaining the relationship between each magnetic head and the off-track amount, Figure 8 is a diagram explaining off-track due to eccentricity of the magnetic disk medium, and Figure 9 is a diagram explaining the deviation due to the conventional analog method. This is a diagram illustrating the method of measuring the rotational off-track amount, in which (a) is the signal pattern of the measurement track, (b) is the output voltage waveform of the magnetic head when there is no off-track, and (c) is when there is off-track. The output voltage waveform of the magnetic head, (d) is (c
) is the amount of off-track calculated from the difference in output voltage. In the figure, 1 is a magnetic disk medium, 2 is a spindle,
3 is a motor, 4 is a magnetic head, 5 is a drive arm, 6 is a positioning mechanism, 7 is a normal center point, 8 is an eccentric center point,
9 is a normal magnetic disk medium, 10 is a track when it is normal, 11 is an eccentric magnetic disk medium, 12 is a track when it is eccentric, 13 is a rotating shaft, 14 is 10 parts, 15 is DATA
16 is an index, 17 is a positioning control unit, 1 is a control unit, 19 is a read/write unit, 20 is a motor drive unit, 21 is an interface unit, 22 is a test device, 23
is a control signal, 24 is an address signal, 25.25a is a read/write signal, 26 is a direct offset signal,
27 indicates a magnetic disk device. Patent applicant: Fujitsu Limited, sub-agent, patent attorney, Yasushi Fukushima 7 years old. Margin ○ Sei 1 Shijijiri (b) Daijo pJ 4th territory (C) (d) Daida#l] Hawk-ki tel Sugugi 纂 5 concave (e) Oba PJ Shigeru 4FI Notification 1 Mr. Rat Suku Housase Nσ Sho-kunku (turning off toe... Nowa series 6 diagrams (a!) 2n footte lg quantity o'7 tofu 4 (b) (C) 6 * @cy = wandering otsuenzentat Head's Sai7 Toe
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Claims (1)

[Claims] In a magnetic disk device, after one track of a magnetic disk medium is divided into n sectors and formatted, and a predetermined environmental stress is applied to the magnetic disk device, the cylinder value increases for each sector. Measure the offset margin of the magnetic head in the forward direction and in the reverse direction where the cylinder value becomes smaller, find the intermediate value between the forward offset margin and the reverse offset margin of each sector, and calculate the intermediate value. The value is the amount of off-track of the magnetic head caused by the deviation of the center of rotation of the magnetic disk medium, and from the amount of change in the amount of off-track for each sector, it is determined that the center of rotation of the magnetic disk medium is shifted due to the environmental stress mentioned above. A method for measuring the amount of whirling off-track of a magnetic disk medium, characterized by determining a change in the amount of off-track caused by deviation.