JP2002367307A - Magnetic disk drive - Google Patents

Abstract

(57) Abstract: Provided is a disk device that realizes seek control that is not affected by an increase or decrease in a Tkul constant due to a temperature change of a VCM when a magnetic head is moved to a desired position on a magnetic disk. A VCM current detector during following is provided.
The current and voltage are detected by the voltage detector 30 between VCM terminals, and AD
The drive controller 5 calculates the output digitally converted in C31, thereby calculating the coil resistance value and the torque constant. The seek loop gain 28 is corrected based on the result, and variation in seek time at the same distance due to temperature change is suppressed.

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 for recording and reproducing information on a magnetic disk by using a magnetic head, and more particularly to a magnetic disk drive having a voice coil motor as driving means for the magnetic head.

[0002]

2. Description of the Related Art FIG. 2 schematically shows a general magnetic disk drive and a method of use. Generally, the magnetic disk device 1 is connected to a host 2 via an interface 3 and executes an operation corresponding to a command from the host 2. For example,
When a write / read command is issued from the host 2,
The interface control unit 4 calculates a track / sector / block length or the like corresponding to the command, and issues the command to the drive control unit 5 via an interface inside the magnetic disk device 1. Upon receiving the command, the drive control unit 5 seeks the magnetic head 6 to a desired track 9 on the magnetic disk 7 and, after following, seeks a desired sector 1.
Write / read is started after reaching 0. Position information (servo) 8 is written on the magnetic disk 7 at an arbitrary position after an arbitrary position on the circumference at an arbitrary constant interval. The contents thereof include a track number 9, a sector number 10, a burst signal, and the like. The track number 9 is written with the same number on the same circumference, and the sector number 10 is written with a value incremented from a reference position (index). These servos 8 are written at arbitrary constant intervals in the radial direction, and the track numbers 9 are incremented or decremented. By reproducing the servo 8 with the magnetic head 6, its own position on the magnetic disk 7 is recognized.

In recent years, in order to effectively utilize the waiting time for arrival at a desired sector 10 after following to a desired track 9, a seek time is delayed until just before the sector 10 is reached, and the seek time is moved at a lower speed to reduce power consumption. Features are starting to be supported.

Also, a function of receiving a plurality of commands from the host 2 and issuing commands to the drive control unit 5 while rearranging the commands by the interface control unit 4 so that the processing speed is the fastest has been supported. These functions are realized by learning the seek time for each moving distance in advance.

Next, the head positioning operation and configuration of a general magnetic disk drive will be briefly described. The disk device 1 records information with a magnetic head 6 on a magnetic disk 7 rotated at a high speed by a spindle motor 11, and
The information recorded by the magnetic head 6 is also reproduced. The magnetic head 6 is connected to the VCM 13 via the actuator 12.
The digital output from the drive control unit 5 is converted to an analog voltage by a digital-to-analog (DA) converter 15, and the analog voltage is supplied to the VCM amplifier 14. A reference voltage is supplied to the VCM amplifier 14, and a current is applied to the VCM 13 in accordance with a difference from the reference voltage, and the VCM amplifier 14 rotates to position the magnetic head 7.

The load / unloading mechanism 16
In the case of the apparatus having the above, when the desired number of rotations is reached, the operation of loading the magnetic head 6 onto the magnetic disk 7 is started. A slider (not shown), on which the magnetic head 6 stopped above the home position 17 is mounted and connected to the VCM 13 via the actuator 12, slides down the ramp 18 by applying a current to the VCM 13, and The magnetic head 6 is loaded on the disk 7.

Next, an outline of head positioning control of a magnetic disk drive by digital control will be described with reference to FIG.

The drive control unit 5 outputs a current instruction value at each interval divided by the servo interval or the servo interval / n, rotates the VCM 13 and controls the positioning of the magnetic head 6.

The drive control unit 5 is constituted by a microprocessor.

The seek control is based on the target position 19 and the position signal 20 from the magnetic head.
1 is set, a target speed 23 is set from the target speed table 22 calculated in advance, and an acceleration FF value 25 is set in the acceleration feedforward (FF) table 24. A speed detector is calculated from the target speed 23 and the position signal 20. 26, the speed gain is multiplied by 27, the acceleration FF value 25 is added thereto, and a seek loop gain multiplied by 28 is obtained as the acceleration (seek current instruction value).
5. A current is applied to the VCM 13 via the VCMAMP 14 to move the magnetic head. FIG. 3 shows the relationship among the applied current (acceleration), speed, and position deviation during seeking. The speed is accelerated until just before reaching the target speed, and after reaching, the speed is reduced according to the seek current value output according to the remaining movement distance.

Although the positioning is performed at the target position by such a method, when seeking at a high speed, a large current is required at the time of acceleration until reaching the target speed and at the time of deceleration from a constant speed or an accelerated state to a desired track. Heat generation, temperature, and coil resistance increase, and torque constant Kf32 decreases. When a seek operation with a large acceleration / deceleration current is repeated, the coil temperature rises significantly. It is expected that the temperature may exceed + 100 ° C. with respect to the normal temperature when the operation which has the most severe seek waiting time for the temperature rise, no constant velocity current section, and the maximum acceleration / deceleration current are repeated. However, since no sensor or the like for grasping an increase in coil resistance and a decrease in Kf32 is provided, the drive control unit 5
Then, the resistance value, K
The target speed table 22, the acceleration FF table 24, and the seek loop gain 28 are set as f32, and the current value is calculated and output.

[0012]

SUMMARY OF THE INVENTION Coil resistance and Kf
32 increases or decreases depending on the coil temperature. Therefore, if a rise in coil temperature is anticipated in advance, a difference between the target acceleration and deceleration occurs due to an increase or decrease in Kf, and as a result, the seek time varies even when moving the same distance. Even if an attempt is made to improve the processing capacity by rearranging the commands from the host 2, the movement time during learning and the actual movement time are different, and a rotation wait occurs, which does not lead to an improvement in the processing capacity. The same can be considered for a command for writing / reading data without waiting for rotation due to low power consumption. In addition, a decrease in Kf27 may cause a case where a desired track cannot be fully decelerated on the target deceleration trajectory, resulting in a seek error.

A load / unload function 16
In an apparatus having a magnetic disk, an operation of unloading the magnetic head from above the magnetic disk is performed.
Although the unloading speed can be detected from the position information 8 above, this method cannot be adopted outside the magnetic disk 7 without the position information 8, so that a method of calculating the unloading speed from the back electromotive voltage of the VCM 13 is used. If the unloading operation is performed without speed control, the speed fluctuates due to the frictional force of the ramp 18, the increase and decrease of the coil resistance value, etc., and stops in the middle of the ramp 18, and the magnetic disk 7 and the magnetic head 6 are stopped.
May come into contact with each other. Similarly, the magnetic head 6 moves at a high speed due to the increase or decrease of the coil resistance value, collides with the stopper, and a shock may be applied to the magnetic head to cause damage. It is also conceivable that the magnetic disk 7 rebounds not only at the home position 17 but also slides down the ramp 18 again and comes into contact with the magnetic head 6.

The above phenomenon can be avoided by controlling the speed by the back electromotive voltage outside the magnetic disk 7. However, since the speed is calculated using a resistance value assuming a temperature rise, an error occurs in the detected speed due to the temperature. The above problems are not completely solved. In order to eliminate these problems, the present invention provides a magnetic disk drive that measures a coil resistance value or a temperature during a following operation without adding a component such as a sensor and performs appropriate seek control and unload control using the result. It is in.

[0015]

During the following operation, the VCM counter electromotive voltage is 0 because the magnetic head 6 does not move. Accordingly, during this time, the voltage between the VCM terminals and the VCM current are measured by the VCM terminal voltage detection circuit 29 and the VCM current detection circuit 30, and the analog-to-digital (AD) converter 3
The VCM coil resistance value can be calculated by taking the calculation into the drive control unit 5 via 1.

Further, the coil temperature can be calculated from an equation representing the temperature characteristics of the coil resistance. Similarly, the current Kf3 is calculated from the calculated temperature using an expression representing the temperature characteristic of Kf32.
2 can also be calculated.

The drive control unit 5 corrects the seek loop gain 28 based on the calculated resistance value and Kf to output a current value, thereby making it possible to reduce variations in seek time. In addition, Kf32
If it is determined that there is a possibility that a seek error may occur due to a decrease in speed and a deceleration cannot be completed, an error can be avoided by advancing the deceleration start position.

Further, by calculating the resistance value during the following, the speed can be detected by the back electromotive force using the resistance value immediately before the start of unloading, so that the speed detection offset is minimized, and the speed detection offset from the target speed is reduced. The deviation of the unloading speed can be prevented, and the contact between the head and the disk and the damage to the head can be prevented.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific method of VCM resistance learning will be described with reference to FIGS. The magnetic head on the magnetic disk not only writes / reads data,
Except during seeking to an arbitrary track, basically following to an arbitrary track is performed.

The voltage between VCM terminals Vvcm33 is expressed by the following equation.

Vvcm = Ivcm.Rm + Vbemf where Ivcm34 is a current flowing through the VCM 14, Rm35.
Is a coil resistance value, and Vbemf36 is a VCM back electromotive voltage.
Since no moving speed occurs during the following, no VCM back electromotive voltage is generated. Therefore, Vbemf = 0, and Vvcm = Ivcm · Rm Rm = Vvcm / Ivcm holds.

Accordingly, the coil resistance value Rm35 can be obtained by the drive control unit from the Vvcm 33 and Ivcm 34 that have been AD-converted during the following.

It is conceivable that Vvcm 33 and Ivcm 34 are small and inaccurate.
6. This can be realized by providing an amplification circuit in the voltage detection circuit 17 between VCM terminals. The amplifier circuit is not specifically described.

The temperature characteristic of the coil resistor Rm43 is generally represented by the following equation (1).

Rm = Rm0 · (1 + K1 · (Temp−Temp0)) (1) where Rm0 is the coil resistance at room temperature, K1 is the temperature characteristic of the coil, Temp is the current coil temperature, and Temp0 is At room temperature. Rm0, Temp0, and K1 are known values, and the coil temperature can be calculated if the current resistance value is known.

The torque constant Kf is generally expressed by the following equation (2).

Kf = Kf0 · (1−K2 · (Temp−Temp0)) (2) where Kf0 is a torque constant at normal temperature, K2 is a temperature characteristic term of the torque constant, Temp is a current coil temperature, Temp0 is at room temperature. Kf0, Temp0, and K2 are known values, and Kf can be calculated as described above.

These calculations are realized by adding the functions of the VCM resistance detector 37 and the Kf detector 38 to the drive control unit.

Next, a specific example for correcting variations in seek time using Kf obtained above will be described.

Generally, VCM 14 is represented by Kf / m. Here, m is a head conversion mass. By applying a potential difference between the VCM terminals and flowing a current (acceleration) I, acceleration and deceleration are performed. Since m has no temperature dependence, the acceleration / deceleration ability is determined by Kf and I. The Kf set temperature at the time of creating the speed control tables 22 and 24 is T0, and the Kf at that time is Kf0.
The seek loop gain 28 is output as a corrected current value by the seek loop gain corrector 40 so that Kf / m * I becomes constant from the Kf_sense 39 calculated by the above-described method. Becomes possible.

In addition, in the above-mentioned correction method as well, in the conventional method, if the temperature becomes higher than the set temperature at the time of creating the seek table, and if the corrected value becomes more than the supply capability of the power supply voltage, the deceleration capability is reduced and a seek error occurs. However, the present invention can be applied to a means for avoiding a seek error by monitoring Kf, grasping the limit of the deceleration ability, and performing processing such as advancing the deceleration start position.

Next, using the coil resistance value and Kf immediately before the start of movement calculated by the above-described method, the value obtained by converting the VCM terminal voltage Vvcm33 during the movement from the AD converter 31 into the drive control unit 5 is calculated by the following equation. The speed is calculated from the back electromotive voltage Vbemf36.

Vvcm = Vbemf + Rm · Ivcm = Kf · Vel + Rm · Ivcm Vel = (Vvcm−Rm · Ivcm) / Kf By performing unload control using this detection speed, a high-precision speed can be obtained even in an area without servo information. Control becomes possible.

[0034]

According to the present invention, it is possible to suppress the variation in the seek time due to the VCM temperature change by calculating the VCM coil resistance value during the following operation, calculating the torque constant based on the calculation result, and correcting the seek system gain. It has become possible.

As a result, seek time learning used for command rearrangement from the host can be optimized, and performance degradation due to rotation waiting can be prevented.

Similarly, since the speed is calculated from the back electromotive force using the VCM resistance value immediately before unloading, the follow-up of the unload target speed in an area where there is no servo information is improved so that contact between the head and the disk can be achieved. The cause of the failure can be eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional seek system by digital control and an additional function unit according to the present invention.

FIG. 2 is a schematic diagram of a magnetic disk drive.

FIG. 3 is a diagram showing an acceleration, a speed, and a position deviation during a seek.

FIG. 4 is a schematic diagram of a circuit for detecting coil resistance and detecting a torque constant according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk device, 2 ... Host, 3 ... Interface, 4 ... Interface control part, 5 ... Drive control part, 6 ... Magnetic head, 7 ... Magnetic disk, 8 ... Position information (servo), 9 ... Track (track number) ), 10 ... sector (sector number), 11 ... spindle motor, 12 ...
Actuator, 13 ... Voice coil motor (VCM),
14 VCM amplifier, 15 Digital-to-analog converter (DA converter), 16 Load / unload mechanism, 17 Home position, 18 Ramp, 19 Target position, 20 Position signal, 21 Moving distance , 22 target speed table, 23 target speed, 24 acceleration FF table, 25 acceleration FF value, 26 speed detector, 27
... speed gain, 28 ... seek loop gain, 29 ... VC
M terminal voltage detection circuit, 30 ... VCM current detection circuit, 3
1: Analogue digital converter (AD converter), 32: Torque constant (Kf), 33: VCM terminal voltage, 34: V
CM current, 35: VCM coil resistance, 36: back electromotive voltage,
37: VCM resistance detector, 38: Kf detector, 39: Kf (Kf_sense) calculated by the drive control unit, 40: seek loop gain corrector.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshio Soyama 2880 Kozu, Odawara-shi, Kanagawa F-term, Hitachi Ltd. Storage Division F-term (reference) 5D096 VV01

Claims (5)

[Claims] 1. A magnetic disk, a spindle motor for rotating the magnetic disk, a spindle motor driver for driving the spindle motor, a head for recording and reproducing information on and from the magnetic disk, and an actuator for moving the head , A voice coil motor (VCM) for rotating the actuator, and a VCM for driving the VCM
Amplifier, means for detecting position information reproduced from the magnetic disk via the head, and a drive control unit for generating a digital output for moving and positioning the head to a desired position based on the reproduced position information A digital-to-analog converter for converting a digital signal from the control unit to an analog output, a circuit for measuring a voltage between VCM terminals, a circuit for measuring a VCM current, and inputting an analog output of the circuit to the control unit In an apparatus having an analog-to-digital (AD) converter that converts a digital signal to a digital signal, a V-track is generated during positioning (following) on a desired track.
A magnetic disk drive characterized in that a VCM resistance value is measured from a current flowing through a CM and a voltage between terminals. 2. The magnetic disk drive according to claim 1, wherein a coil temperature of the VCM is calculated from the detected resistance value, and a torque constant is measured. 3. The magnetic disk drive according to claim 1, wherein the gain of the seek control system is corrected using the measured resistance value and torque constant to suppress variations in seek time. 4. The method according to claim 1, wherein the moving speed obtained from the back electromotive voltage of the VCM during the movement of the head is corrected without being affected by a change in the temperature of the VCM. The magnetic disk drive according to claim 1. 5. The magnetic disk drive according to claim 1, wherein
If the magnetic head has a function of retracting (unloading) or loading from the magnetic disk,
2. The magnetic disk drive according to claim 1, wherein the detection speed according to claim 4 is used for unload speed control.