JP2002050139A - Device for positioning magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time for positioning a magnetic head by reducing the influence of the fluctuation of torque generated in a voice coil motor. SOLUTION: A deviation detecting means detects the deviation of position of a magnetic head detected by a position detection means and a target orbit generated by a target orbit generating means. A servo compensation means controls the driving current of a driving amplifier so as to reduce the deviation detected by the deviation detecting means. A positive compensation means controls the driving current of the driving amplifier so as to accelerate the motion of a mechanical mechanism on the basis of the target orbit generated by the target orbit generating means. A learning means detects the fluctuation of torque generated in the voice coil motor of the mechanical mechanism from the deviation detected by the deviation detecting means, and controls the gain of the servo compensation means and the positive compensation means according to the fluctuation of the detected torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head positioning apparatus for writing / reading signals to / from a magnetic disk, and more particularly to a hard disk drive (HDD), a servo track writer (STW), and a certifying test of a hard disk drive. The present invention relates to a magnetic head positioning device used in a magnetic disk inspection device that performs the inspection.

[0002]

2. Description of the Related Art In recent years, hard disk devices have been generally used as information recording media for computer systems. Servo tracks for controlling the position of a magnetic head are previously set on a magnetic disk in a hard disk drive by a servo track writer. When a servo track writer sets a servo track on a magnetic disk in a hard disk drive, there are an external drive method and a self-drive method for positioning the magnetic head, which will be described with reference to FIG.

FIG. 4A is an external view of an externally driven servo track writer and a hard disk drive.
The hard disk device 110 includes a plurality of magnetic disks 11
One and a plurality of magnetic heads 112;
Reference numeral 12 is attached to the tip of each support arm of the carriage mechanism 113, respectively. The carriage mechanism 113
A voice coil motor (VCM), not shown, is provided for rotating the support arm to position the magnetic head 112. When setting a servo track, an appropriate bias current is supplied to the voice coil motor of the carriage mechanism 113 so that the magnetic head 112
Is stopped near the outer circumference of.

On the other hand, a guide pin 121 and a mirror 122 are provided on a drive arm of an external actuator 120 constituting a servo track writer. When setting the servo track, the guide pin 121 is connected to the carriage mechanism 1.
13 is mechanically brought into contact with the side surface of the support arm 13, and the drive arm is moved by a voice coil motor built in the external actuator 120 to rotate the carriage mechanism 113. At this time, the laser length measuring device 123
The mirror 122 is provided at an appropriate position facing the mirror 122.
The amount of movement of the drive arm of the external actuator 120 is measured based on the reflected light. External actuator 120
Controls the built-in voice coil motor so that the moving amount becomes a predetermined value based on the measurement result of the laser length measuring device 123, and performs the positioning of the magnetic head 112. Incidentally, Japanese Patent Application Laid-Open No. Hei 5-334822 discloses a technique related to the improvement of this method.
There is one described in Japanese Patent Publication No. A system called an optical push pin system in which the carriage mechanism 113 is guided in a non-contact manner using a laser optical system without using the mechanical contact by the externally driven guide pin 121 shown in FIG. There is also.

FIG. 4B is an external view of a self-drive type servo track writer and a hard disk drive. Components having the same configuration as in FIG. 4A are denoted by the same reference numerals, and description thereof will be omitted. In this method, when setting a servo track, the magnetic head 112 is positioned by the carriage mechanism 113 of the hard disk drive 110 itself without using an external actuator. A mirror 132 is provided above the support arm of the carriage mechanism 113, and a laser length measuring device 133 is provided at an appropriate position facing the mirror 132. The laser length measuring device 133 measures the movement amount of the support arm of the carriage mechanism 113 based on the reflected light from the mirror 132. A VCM control circuit (not shown) controls the voice coil motor of the carriage mechanism 113 based on the measurement result of the laser length measuring device 133 so that the movement amount becomes a predetermined value, and performs positioning of the magnetic head 112. Incidentally, Japanese Patent Laid-Open No.
There is one described in JP-A-6530.

[0006] In any of the positioning methods described above, it is important to shorten the positioning time in order to increase the speed. The shortening of the positioning time is important not only for the servo track writer but also for the hard disk device itself and the magnetic disk inspection device for performing the certifying inspection of the hard disk device. Incidentally, Japanese Patent Application Laid-Open No. 10-27 discloses a magnetic disk inspection apparatus.
There is one described in JP-A-5434.

[0007]

In any of the above-described positioning methods, a voice coil motor is used as a drive unit for positioning the magnetic head. The voice coil motor generates a torque according to the drive current, and the control is generally performed on the assumption that the torque constant of each voice coil motor is constant. However, the torque generated by the voice coil motor slightly varies depending on the position of the magnetic head even when the drive current is the same. Also, the generated torque fluctuates by about 10% depending on the product variation and the aging of the voice coil motor. If the torque generated by the voice coil motor fluctuates, when positioning the magnetic head, an overshoot in which the magnetic head passes the target position (track) or an undershoot that does not reach the target position (track) occurs, and the positioning time is reduced. It causes delay.

[0008] Such a problem is not limited to the servo track writer, but has a similar problem in the hard disk device itself and in the magnetic disk inspection device for performing the certifying inspection of the hard disk device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic head positioning apparatus that reduces the influence of fluctuations in the torque generated by a voice coil motor and has a short positioning time.

[0010]

According to a first aspect of the present invention, there is provided a magnetic head positioning apparatus comprising: a mechanical mechanism for positioning a magnetic head at a predetermined position on a magnetic disk by using a voice coil motor; A drive amplifier for supplying a drive current to the voice coil motor of the mechanism;
What is claimed is: 1. A magnetic head positioning apparatus comprising: a position control unit that controls a drive current of a drive amplifier, wherein the position control unit generates a position detection unit that detects a position of the magnetic head and a target trajectory of the position of the magnetic head. Target trajectory generating means, a deviation detecting means for detecting a deviation between the position of the magnetic head detected by the position detecting means and the target trajectory generated by the target trajectory generating means, and a deviation detected by the deviation detecting means being small. Servo compensating means for controlling the drive current of the drive amplifier so that the forward compensation means for controlling the drive current of the drive amplifier so as to accelerate the movement of the mechanical mechanism based on the target trajectory generated by the target trajectory generation means The fluctuation of the torque generated by the voice coil motor of the mechanical mechanism is detected from the deviation detected by the deviation detecting means, and the servo compensation is performed according to the detected fluctuation of the generated torque. It is obtained by a learning means for controlling a gain of means and forward compensation means.

According to the present invention, the gain of the servo compensating means and the forward compensating means can be controlled so as to correct the fluctuation of the generated torque by the learning means, so that the influence of the fluctuation of the generated torque of the voice coil motor is reduced. In addition, the positioning time can be reduced.

According to a second aspect of the present invention, in the magnetic head positioning apparatus according to the present invention, the learning means calculates the cumulative deviations for two predetermined periods from the deviation detected by the deviation detecting means, and calculates the two calculated deviations. The change in the torque generated by the voice coil motor of the mechanical mechanism is detected from the difference between the accumulated deviations.

According to the present invention, the amount of information is increased and the detection error can be removed by using the cumulative deviation.
Fluctuations in the generated torque can be correctly detected. Also, even if a certain external force is applied to the mechanical mechanism,
By taking the difference between the two deviations, the effect of the external force can be eliminated.

According to a third aspect of the present invention, in the magnetic head positioning apparatus according to the present invention, the learning means has a correction coefficient for changing the gains of the servo compensation means and the forward compensation means.
The correction coefficient is corrected using a value obtained by multiplying the difference between the two cumulative deviations by the safety coefficient.

According to the present invention, the correction coefficient is corrected by using the value obtained by multiplying the difference between the cumulative deviations by the safety coefficient,
The gains of the servo compensator and the forward compensator gradually change. Therefore, even if there is a detection error or a calculation error of the fluctuation of the generated torque, the apparatus does not run away and the magnetic head can be positioned at the target position (track).

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an embodiment of a magnetic head positioning apparatus according to the present invention. This embodiment shows a case in which the present invention is applied to an external drive type servo track writer. A mechanical mechanism (hereinafter abbreviated as a mechanical mechanism) 100 for mechanically positioning a magnetic head is a magnetic disk shown in FIG. 111, magnetic head 112, carriage mechanism 113, guide pin 121, mirror 122,
2 shows a portion including a drive arm of an external actuator 120 and a built-in voice coil motor.

A drive current 140 a is supplied from a drive amplifier 140 to the built-in voice coil motor of the mechanical mechanism 100. The position control unit 200 that controls the drive current 140a of the drive amplifier 140 includes a target trajectory generation unit 210, a deviation detection unit 220, a servo compensation unit 230, a forward compensation unit 240, a learning unit 250, and a position detection unit 260. The position detecting means 260 includes the laser length measuring device 123 shown in FIG.

First, the operation of the other components in FIG. 1 except for the learning means 250 will be described. At the time of setting the servo track, the target trajectory generating means 210 which has received the operation command 310a from the microprocessor unit 310 generates a target trajectory of the position of the magnetic head, and outputs the target trajectory signal 210a to the deviation detecting means 220 and the forward compensating means 240. I do. The forward compensating means 240 for performing feed-forward control of the mechanical mechanism 100 has a drive current 140 of the drive amplifier 140 based on the target trajectory signal 210a from the target trajectory generating means 210 so as to accelerate the movement of the mechanical mechanism 100.
A feedforward signal 240a for controlling a is generated.

On the other hand, the deviation detecting means 220 receives the head position signal 260a from the position detecting means 260 and the target trajectory signal 210a from the target trajectory generating means 210 and receives the deviation between the position of the magnetic head and the target trajectory. And outputs a deviation signal 220a to the servo compensation means 230. The servo compensating means 230 for performing feedback control of the mechanical mechanism 100 includes a deviation signal 220 from the deviation detecting means 220.
a so that the deviation between the position of the magnetic head and the target trajectory becomes smaller based on the driving current 140a of the driving amplifier 140.
Is generated.

The driving amplifier 140 includes the forward compensating means 24
A drive current 140a is generated based on the feedforward signal 240a from 0 and the feedback signal 230a from the servo compensator 230, and is supplied to the built-in voice coil motor of the mechanical mechanism 100. Thereby, the mechanical mechanism 1
No. 00 drives the built-in voice coil motor to position the magnetic head to a target position (track). The position detecting means 260 detects the position of the magnetic head at this time,
The head position signal 260a is output to the deviation detecting means 220.

FIG. 2A shows an example of the position of the magnetic head, and FIG. 2B shows an example of the deviation between the position of the magnetic head and the target trajectory. In FIG. 2A, the broken line shows an example of the target trajectory generated by the target trajectory generating means 210 when the target value of the moving position of the magnetic head is 0.5 μm, and the solid line shows the position detected by the position detecting means 260 in this case. An example of the detected position of the magnetic head is shown. The solid line in FIG. 2B shows an example of the deviation between the position of the magnetic head and the target trajectory detected by the deviation detecting means 220 in this case.

Next, the operation of the learning means 250 will be described with reference to FIG. The learning means 250 includes the deviation detecting means 220
Of the built-in voice coil motor of the mechanical mechanism 100 on the basis of the deviation signal 220a from the servo mechanism 230, and the servo compensation means 230
And calculates a correction coefficient Mg for changing the gain of the forward compensation means 240, and outputs a correction signal 250a to the servo compensation means 230 and the forward compensation means 240.

The calculation process of the correction coefficient at this time will be described with reference to FIG. FIG. 3 is a flowchart illustrating the calculation process of the correction coefficient. The learning means 250 first sets the correction coefficient Mg to an initial value (Step 510). The initial value is a value when there is no change in the generated torque of the built-in voice coil motor of the mechanical mechanism 100, for example, Mg = 1. The position control unit 200 controls the mechanical mechanism 10 via the drive amplifier 140.
0 is driven to perform the positioning operation of the first one track (step 520). At this time, the deviation detecting means 220
A deviation between the position of the magnetic head detected by the position detection means 260 and the target trajectory generated by the target trajectory generation means 210 is detected, and a deviation signal 220a is output.

The learning means 250 calculates accumulated deviations A and B for two predetermined periods from the deviation signal 220a (step 530). For example, in the case of the deviation in FIG. 2B, the hatched portions indicate the accumulated deviations A and B for the predetermined time T1, respectively. Here, the cumulative deviation is used.
This is because, when the deviation is small, the amount of information is increased and the fluctuation of the generated torque is correctly detected. Further, the position detecting means 2
This is for removing a detection error generated by the detection accuracy of 60 and correctly detecting a fluctuation of the generated torque.

Subsequently, the learning means 250 determines whether or not the difference between the two cumulative deviations A and B is within a predetermined value (step 54).
0). Here, to see the difference between the two cumulative deviations A and B,
This is because even if a constant external force is applied to the mechanical mechanism 100, the influence of the external force can be eliminated by taking the difference between the two deviations.

If the difference between the two cumulative deviations A and B is not within the predetermined value in step 540, the learning means 250
g is corrected (step 550). The correction of the correction coefficient Mg is performed by, for example, the following expression: Mg [n + 1] = 0.5 k (A−
B) + Mg [n] is used. In this equation, Mg [n], M
g [n + 1] indicates an n-th correction coefficient and an (n + 1) -th correction coefficient, k indicates a torque variation coefficient, and 0.5 indicates a safety coefficient. The reason for multiplying the safety factor is that if there is a detection error or a calculation error in the fluctuation of the generated torque, the apparatus may run out of control and cannot be positioned at the target position (track). This is because the change in the gain is moderated to prevent this. Note that the safety coefficient is not necessarily limited to 0.5, and a value less than 1
It can be used as appropriate according to the motion characteristics of 00 and the detection accuracy of the position detecting means 260.

If the difference between the two cumulative deviations A and B is within a predetermined value in step 540, or after correcting the correction coefficient Mg in step 550, the position control unit 200 determines whether or not the next track needs to be positioned. A determination is made (step 560).
Step 520 if positioning of the next track is required
The process returns to the step, and terminates the processing if not necessary.

Returning to the description of FIG. 1, at the time of the next track positioning operation, the forward compensating means 240 uses the learning means 250 when generating the feedforward signal based on the target trajectory signal 210a from the target trajectory generating means 210. , The gain is changed based on the correction signal 250a to correct the feedforward signal, and the corrected feedforward signal 240a is output to the drive amplifier 140. Further, when creating the feedback signal based on the deviation signal 220a from the deviation detection unit 220, the servo compensation unit 230 corrects the feedback signal by changing the gain based on the correction signal 250a from the learning unit 250, and The corrected feedback signal 230a is output to the amplifier 140. The drive amplifier 140 includes a corrected feedforward signal 240a from the forward compensation means 240 and a corrected feedback signal 2 from the servo compensation means 230.
A drive current 140a is generated based on 30a and supplied to a built-in voice coil motor of the mechanical mechanism 100. Thereby, the mechanical mechanism 100 drives the built-in voice coil motor with the drive current 140a corrected by the correction coefficient Mg of the learning means 250, and performs positioning of the magnetic head to the target position (track).

Each of the embodiments described above shows a case where the magnetic head positioning apparatus of the present invention is applied to an externally driven servo track writer. However, the present invention is not limited to this, and can be applied to self-drive type or optical push-pin type servo track writers, as well as hard disk devices themselves and magnetic disk inspection devices. In each case, the mechanical mechanism 100 replaces the corresponding part of each device.

[0030]

According to the magnetic head positioning apparatus of the present invention, the gain of the servo compensating means and the forward compensating means can be controlled by the learning means so as to correct the fluctuation of the torque generated by the voice coil motor of the mechanical mechanism. Therefore, the influence of the fluctuation of the generated torque of the voice coil motor can be reduced, and the positioning time can be shortened.

Further, by detecting the fluctuation of the generated torque of the voice coil motor of the mechanical mechanism from the difference between the accumulated deviations of the two predetermined periods, the fluctuation of the generated torque can be correctly detected, and the influence of the external force is also eliminated. be able to.

Further, by correcting the correction coefficient using a value obtained by multiplying the difference between the two cumulative deviations by the safety coefficient, the apparatus does not run away even if there is a detection error or a calculation error of the fluctuation of the generated torque. The magnetic head can be positioned at a target position (track).

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a magnetic head positioning device according to the present invention.

FIG. 2A is a diagram illustrating an example of a position of a magnetic head, and FIG. 2B is a diagram illustrating an example of a deviation between the position of the magnetic head and a target trajectory.

FIG. 3 is a flowchart illustrating a calculation process of a correction coefficient.

FIG. 4A is an external view of an externally driven servo track writer and a hard disk drive, and FIG.
1 is an external view of a self-drive type servo track writer and a hard disk drive.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 mechanical mechanism 110 hard disk device 111 magnetic disk 112 magnetic head 113 carriage mechanism 120 external actuator 140 drive amplifier 200 position control unit 210 target trajectory generating unit 220 deviation detecting unit 230 servo compensating unit 240 ... Forward compensation means 250... Learning means 260... Position detection means 310.

Claims (3)

[Claims] 1. A mechanical mechanism for positioning a magnetic head at a predetermined position on a magnetic disk using a voice coil motor, a drive amplifier for supplying a drive current to a voice coil motor of the mechanical mechanism, and a drive current for the drive amplifier A position control unit for controlling a position of the magnetic head, wherein the position control unit includes: a position detection unit that detects a position of the magnetic head; and a target trajectory generation unit that generates a target trajectory of the position of the magnetic head. Means, a deviation detection means for detecting a deviation between the position of the magnetic head detected by the position detection means and the target trajectory generated by the target trajectory generation means, and the deviation detected by the deviation detection means is reduced. Servo compensating means for controlling the drive current of the drive amplifier, and the target trajectory generated by the target trajectory generating means, Forward compensation means for controlling the drive current of the drive amplifier so as to accelerate the movement of the mechanical mechanism; and detecting and detecting fluctuations in the torque generated by the voice coil motor of the mechanical mechanism from the deviation detected by the deviation detection means. A magnetic head positioning device comprising: a learning unit that controls gains of the servo compensation unit and the forward compensation unit in accordance with the generated torque fluctuation. 2. The learning means calculates respective cumulative deviations for two predetermined periods from the deviation detected by the deviation detecting means, and generates a voice coil motor of the mechanical mechanism from the difference between the two calculated cumulative deviations. 2. The magnetic head positioning device according to claim 1, wherein a change in torque is detected. 3. The learning means has a correction coefficient for changing gains of the servo compensation means and the forward compensation means, and uses a value obtained by multiplying a difference between the two cumulative deviations by a safety coefficient. 3. The method according to claim 2, wherein
3. The magnetic head positioning device according to claim 1.