JP2795998B2 - Speed control device for magnetic disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed controller for a magnetic disk drive (HDD) using a servo system.

[0002]

2. Description of the Related Art Conventionally, positioning control of a magnetic head in a magnetic disk drive includes access control for moving the magnetic head to a target track and track following control for positioning the magnetic head at the center of the target track. is there. The access control controls the moving speed of the magnetic head, and is therefore called speed control.

In the speed control, a target speed corresponding to a distance until the magnetic head reaches a target track is set in advance, and an operation is performed such that the actual moving speed of the magnetic head matches the set target speed. Will be In general, the current position of the magnetic head is sequentially detected along with the movement of the magnetic head, and the actual moving speed value is obtained by calculation, and a value obtained by subtracting the target speed value from the moving speed value, that is, the target speed value A difference speed value indicating the difference between the moving speed value and the moving speed value is fed back to the speed control output. That is, closed loop control is performed.

[0004]

However, in the closed loop control, the moving time of the magnetic head differs depending on whether the differential speed value is positive or negative. That is, when the differential velocity value is positive, the time required for the magnetic head to move to the target track, that is, the moving time, is shorter than the target moving time. When the differential speed value is negative, the moving time of the magnetic head is longer than the target moving time. Therefore, even if the accuracy of the speed control, that is, the absolute value of the differential speed value is equal, the moving time differs depending on the positive / negative of the differential speed value, and the original purpose is to shorten and stabilize the moving time of the magnetic head. There is a problem that is damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a magnetic disk drive speed control apparatus capable of stably moving a magnetic head and shortening the moving time of the magnetic head. And

[0006]

According to the present invention, in a deceleration control phase in speed control, a gain is switched according to the polarity of an error between a target speed and a moving speed (actual speed). In this case, when the moving speed is lower than the target speed, the gain is increased, and when the moving speed is higher than the target speed, the gain is decreased.

Further, the present invention feeds back an error between a target speed and a moving speed as a function of a moving elapsed time to a control output.

[0008]

According to the above-described structure, the reduction and stabilization of the moving time, which is the purpose of the original speed control, is added to the target function of the control.
It is possible to prevent the moving time of the head from increasing. As a result, stabilization and shortening of the traveling time are realized.

[0009]

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

First, before describing an embodiment of the present invention, a problem of speed control in positioning control of a magnetic disk drive will be described with reference to FIGS.

The positioning control of the magnetic head in the magnetic disk drive includes speed control for moving the magnetic head to a target track and track following control for positioning the magnetic head at the center of the target track. In the speed control, a target speed corresponding to a distance until the magnetic head reaches the target track is set in advance,
An operation is performed such that the actual moving speed of the magnetic head matches the set target speed.

A target speed curve as a function of the moving time or moving distance of the magnetic head is also called a speed profile curve.
Shown in In the figure, a is a positive acceleration, and b is a negative acceleration. Speed control is performed for each of the acceleration period AP, the constant speed period CP, and the deceleration period DP as shown in FIGS. 8 and 9. In the acceleration period AP, the magnetic head is accelerated by a constant positive acceleration a (corresponding to the maximum acceleration) until the moving speed of the magnetic head reaches the target speed Vmax in the constant speed period CP. In the constant speed period CP, the target speed Vmax is maintained. In the deceleration period DP, the magnetic head is decelerated by a constant negative acceleration b (corresponding to 1/2 to 1/3 of the maximum acceleration).

Here, in the deceleration period DP, the magnetic head moves to the target track at a constant negative acceleration b. Accordingly, by sequentially detecting the current track position of the magnetic head with the movement of the magnetic head, the actual moving speed value of the magnetic head is obtained, and the differential speed value indicating the difference between the target speed value and the moving speed value is obtained. Is fed back to the speed control output. That is, closed loop control is performed.

In the speed control, it is desired to move the magnetic head stably and at high speed until the magnetic head reaches the target track. For example, as shown in FIG. 10, in the control A, during the deceleration period DP of the target speed profile curve as a function of the moving distance until the magnetic head reaches the target track, in the control A, the moving speed value of the magnetic head is different from the target speed value. Is repeatedly increasing and decreasing. In the control B, the moving speed value is always higher than the target speed value. Further, in the control C, the moving speed value is smaller than the target speed value except for a period immediately after the start of the deceleration period DP. As described above, the moving speed value variously changes with respect to the target speed value depending on the speed control method. here,
The moving time Ts of the magnetic head is expressed by the following equation (1).

[0015]

(Equation 1) X0 is the track position of the target track, V0 is the target speed, V is the moving speed, ΔV is the target speed V0 and the moving speed V
And is defined as (V-V0).

As described above, when the value of the differential velocity ΔV is positive, the movement time Ts, which is the time from the start of movement of the magnetic head to the arrival at the target track, is shorter than the target movement time. When the value of the differential speed ΔV is negative, the movement time Ts becomes longer than the target movement time. Therefore, even if the accuracy of the speed control, that is, the absolute value of the differential speed value is equal, the moving speed differs depending on whether the differential speed value is positive or negative. The reason is that the moving time of the magnetic head has not been used as a target value in the feedback control.

Therefore, in the present invention, in order to shorten and stabilize the moving time of the magnetic head, during the deceleration period of the speed control, the positive / negative value of the difference speed indicating the difference between the target speed and the moving speed is determined. The gain for the control output is switched accordingly. Further, the value of the differential speed relating to the moving distance and the moving time is fed back to the control output. Hereinafter, a first embodiment of the present invention will be described.

The speed control model of the first embodiment shown in FIG. 1 includes a position detecting section 21, a target speed generating section 22, a moving speed calculating section 23, subtracting sections 24 and 28, a compensation filter section 25, a gain controlling section 26, It is configured by a control target 27.

A position detector 2 represented by a transfer function H (s)
1 detects the controlled variable X output from the control target 27 represented by the transfer function G (s). Moving speed calculator 23
Calculates the moving speed value Va based on the moving position Xa output from the position detecting unit 21. The subtractor 28 obtains the difference between the target position XR and the movement position Xa, that is, the remaining movement distance Xe. The target speed generation unit 22 calculates a target speed value V corresponding to the remaining movement distance Xe output from the subtraction unit 28.
Generate R. The subtractor 24 subtracts the moving speed value Va from the target speed value VR to obtain a difference speed value Ve indicating the result of the subtraction. The compensation filter unit 25 represented by the transfer function C (s) performs, for example, an integral compensation operation and a phase compensation operation on the differential velocity value Ve. Gain control unit 26
Supplies an operation amount u obtained by controlling the gain K with respect to the differential speed value Ve to the control target 27.

As can be seen from the gain characteristic of the gain control unit 26 shown in FIG. 2, when the differential speed value Ve> 0, that is, when the moving speed value Va is smaller than the target speed value VR, the gain control unit 26 The gain K is set to Kp.
On the other hand, when the differential speed value Ve <0, that is, when the moving speed value Va is larger than the target speed value VR, the gain K of the gain control unit 26 is set to Kn. In addition, Kp>
Kn.

Therefore, when the moving speed value is smaller than the target speed value, the speed following performance to the target speed can be improved by setting the gain to a high gain Kp. Also,
If the moving speed value is larger than the target speed value, the low gain K
By setting n, the speed following can be stabilized.

FIG. 3 is a diagram showing the configuration of the speed control device of the first embodiment corresponding to the speed control model shown in FIG.
In FIG. 3, a magnetic disk 10, which is a recording medium,
It is formatted so as to be used in a magnetic disk drive of the sector servo system. Both the front and back surfaces of the magnetic disk 10 are data surfaces for recording information,
Each data surface is provided with a track for recording information on a concentric circle. Further, each track is divided into a plurality of sectors. Each sector is divided into a servo area in which servo information for positioning the magnetic head 11 is recorded in advance, and a data area in which a user reads / writes data. In the servo area, track address information indicating the absolute position of the track on which the sector exists and burst information for positioning the magnetic head 11 at the center of the track on which the sector exists are recorded in advance.

After the magnetic head 11 reads the burst information from the magnetic disk 10 and performs signal processing, an analog signal indicating how much the magnetic head 11 deviates from the center of the track is obtained. In this analog signal, the voltage value indicates the amount of displacement of the magnetic head 11, and the polarity indicates the direction of the displacement. The track address information is used for controlling the speed of the magnetic head 11, and the burst information is used for controlling the track following of the magnetic head 11. The details of the burst information for positioning the magnetic head 11 are described in US Pat.
No. 94,469.

Although not described in detail, the magnetic disk 1
0 is rotationally driven by the spindle motor 10a.
Further, although only one magnetic head 11 is shown for convenience, two magnetic heads 11 are provided so as to face both surfaces of the magnetic disk 10.
Needless to say, it may be provided and attached to the carriage 20.

The magnetic head 11 records / reproduces data on / from the magnetic disk 10. The amplifier 12 amplifies a reproduction signal from the magnetic head 11. Position detector 13
Detects the position (in other words, the track number) of the track where the magnetic head 11 is currently located, based on the track address information of the servo data included in the amplified reproduction signal, and outputs it to the CPU 15. Further, the position detector 13 detects the magnetic head 11 based on the burst information of the servo data included in the amplified reproduced signal.
A / D (analog / dig) converts the analog signal corresponding to the deviation amount from the center of the track where the current position is located.
ital) to the converter 14. A / D converter 14
Digitizes the amount of displacement of the magnetic head 11 with respect to the center of the track based on the input analog signal,
15 is output.

CPU (central processing unit) 15
Performs control of the entire apparatus, gain switching according to the positive / negative differential speed value, compensation calculation, and the like. ROM (read only memor
y) 16 has a storage unit 16a for storing data necessary for speed control. The storage unit 16a stores the magnetic head 1
Speed data indicating a target speed profile curve corresponding to one moving distance is stored in advance. D / A (digital / an
alog) The converter 17 converts a control signal output from the CPU 15 into an analog signal. Power amplifier 18 amplifies the control signal converted to an analog signal.

The voice coil motor (VCM) 19 drives the carriage 20 based on the control signal amplified by the power amplifier 18. The carriage 20 supporting the magnetic head 11 is driven by the VCM 19 to move the magnetic head 11. As a result, the magnetic head 11 moves to the target track position of the magnetic disk 10.

Next, the operation of the speed control device shown in FIG. 3 will be described.

When reading / writing data from / to the magnetic disk 10, the magnetic head 11 moves on the magnetic disk 10 toward a target track to be read / written. The magnetic head 11 reads the servo data recorded on the magnetic disk 10 in advance with the movement. The read servo data is amplified by the amplifier 12 and then input to the position detector 13.

During the deceleration period of the speed control, the position detector 13 detects position data (track address information) indicating the track on which the magnetic head 11 is currently located from among the servo data read from the magnetic disk 10 by the magnetic head 11.
Is detected and output to the CPU 15.

The operation of the CPU 15 will now be described with reference to the flowchart shown in FIG.

In step A1, the CPU 15 receives the track address information as the position data output from the position detector 13.

In step A2, the CPU 15 calculates the moving speed of the magnetic head 11 based on the received position data. That is, the position data is generated by the servo data read from the magnetic disk 10 every one sector time. 2 read continuously during the movement of the magnetic head 11
The movement distance of the magnetic head 11 is obtained by subtracting two position data obtained by two pieces of servo data. By dividing the obtained moving distance by the sample time (one sector time), the moving speed per one sector time is calculated. One sector time is a time obtained by dividing the time required for the magnetic disk to make one revolution by the number of sectors per track, and the time during which the magnetic head can read servo data from the servo area during the movement. It is an interval.

In step A3, the number of remaining tracks is obtained based on the current track position of the magnetic head 11 and the track position of the target track.
Based on the speed data indicating the speed profile curve stored in advance in 6a, the target speed required for the magnetic head 11 to move the distance corresponding to the obtained number of remaining tracks is calculated.

In step A4, a difference speed value Ve indicating the result of the subtraction is obtained by subtracting the moving speed value from the target speed value. Gain switching in speed control is performed according to the positive / negative of the obtained differential speed value Ve.

In step A5, the differential speed value Ve> 0
, That is, when the moving speed value is smaller than the target speed value, high gain switching is performed (step A).
6) The control signal u corresponding to the differential speed value is output from the CPU 15 with a high gain KH (step A8). That is, the control signal is expressed by u = KH · Ve.

On the other hand, in step A5, the differential speed value V
If e <0, that is, if the moving speed value is larger than the target speed value, low gain switching is performed (step 7), and a control signal u corresponding to the differential speed value is output from the CPU 15 with a low gain KL. (Step A8). The control signal is represented by u = KL · Ve.

The control signal u output from the CPU 15 is
After being converted into an analog signal by the D / A converter 17 and amplified by the power amplifier 18, it is supplied to the VCM 19.

As described above, when the moving speed value is smaller than the target speed value, the time during which the moving speed value falls below the target speed value can be shortened by the high gain control signal. Also, when the moving speed value is larger than the target speed value,
With the low gain control signal, the time during which the moving speed value exceeds the target speed value can be extended. Therefore, by switching the gain in the speed control according to the positive / negative of the differential speed, control is performed so that the moving speed of the magnetic head matches the target speed, and the moving time of the magnetic head can be reduced. .

Next, a second embodiment of the present invention will be described.

The speed control model of the second embodiment shown in FIG. 5 includes a position detecting section 31, a moving speed calculating section 32, and a subtracting section 3.
3, 37, 38, target speed generation units 34, 36, time generation unit 35, gain control units 39, 40, 42, addition unit 41, and control target 43.

The position detector 31 represented by the transfer function H (s) detects the controlled variable X output from the control target 43 represented by the transfer function G (s). Moving speed calculator 32
Calculates the moving speed value Va based on the moving position Xa output from the position detecting unit 31. The subtraction unit 33 acquires the difference between the target position XR and the movement position Xa, that is, the remaining movement distance Xe. The target speed generation unit 34 generates a target speed value VRX corresponding to the remaining moving distance Xe. The time generator 35 generates an elapsed time t from the start of the movement of the magnetic head. The target speed generation unit 36 generates a target speed value VRt corresponding to the elapsed time t. The subtracting unit 37 acquires a difference speed value Vex indicating a difference between the target speed value VRx from the target speed generating unit 34 and the moving speed value Va from the moving speed calculating unit 32. The subtraction unit 38 acquires a difference speed value Vet indicating a difference between the target speed value VRt from the target speed generation unit 36 and the movement speed value Va from the movement speed calculation unit 32. Gain control unit 39
Multiplies the difference speed value Vex from the subtraction unit 37 by α. The gain control unit 40 multiplies the difference speed value Vet from the subtraction unit 38 by β. The adding unit 41 includes a differential speed value Vex multiplied by α in the gain control unit 39 and a differential speed value Vet multiplied by β in the gain control unit 40.
Is added to obtain an addition difference speed value Vea indicating the addition result. The gain control unit 42 supplies an operation amount u obtained by controlling the gain K to the added differential speed value Vea to the control target 43.

As described above, the difference speed value Vex obtained as a function of the movement distance and the difference speed value Vet obtained as a function of the movement time are added at a predetermined ratio, and the difference value Ve indicating the result of the addition is added to the addition difference speed value Ve. On the other hand, by controlling the gain K, the moving time of the magnetic head can be reduced. This is for the following reasons. That is, in the speed control, it is desired to move the magnetic head to the target track in a short time. However, conventionally, speed control has been performed such that the actual moving speed of the magnetic head matches the target speed obtained based only on the moving distance of the magnetic head. Therefore, for example, when the moving speed value is higher than the target speed value, speed control is performed to reduce the moving speed value, despite the fact that the target track can be reached earlier. This is because time increases.

From the above, in the second embodiment,
Since speed control is performed not only according to the moving distance but also according to the moving time, control is performed to make the moving time of the magnetic head coincide with the target moving time, so that the moving time can be shortened and stabilized.

FIG. 6 shows a speed control device according to a second embodiment corresponding to the speed control model shown in FIG. Compared to the device shown in FIG.
b, and a target speed is obtained based on a speed profile curve indicating a target speed corresponding to a moving distance to a target track and a speed profile curve corresponding to an elapsed time from the start of movement of the magnetic head. . The speed data indicating the speed profile curve according to the elapsed time from the start of the movement is stored in the storage unit 16b.

Here, the operation of the CPU 15 in the speed control device shown in FIG. 6 will be described with reference to the flowchart shown in FIG.

In step B1, during the deceleration period of the speed control, the position data for each one sector time outputted from the position detector 13 via the A / D converter 14 is received.

In step B2, the moving speed of the magnetic head 11 is calculated based on the received position data.

In step B3, a target speed value corresponding to the moving distance to the target track is read from the storage section 16a of the ROM 16 based on the received position data. In step B4, a difference speed value Vex indicating the difference between the read target speed value and the calculated moving speed value is obtained.

In step B5, the target speed value corresponding to the elapsed time from the start of the movement of the magnetic head 11 is read from the storage section 16b of the ROM 16 based on the received position data. In step B6, a difference speed value Vet indicating the difference between the read target speed value and the calculated moving speed value is obtained.

In step B7, the calculated differential speed values Vex and Vet are set at a predetermined ratio, for example, α: β = 1:
1 to obtain an addition difference speed value Vea indicating the addition result. In step B8, a control signal corresponding to the added differential speed value Vea is output with a gain K.

The output control signal is supplied to the D / A converter 17.
After being converted into an analog signal by the power amplifier 18 and amplified by the power amplifier 18, the signal is supplied to the VCM 19.

In this embodiment, as compared with the conventional speed control in which the target speed curve is a function of only the moving distance to the target track, the target speed curve is not only the moving distance but also the magnetic head. By using the speed control which is a function of the elapsed time from the start of the movement, the movement time of the magnetic head can be reduced and stabilized.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention.

The present invention is not limited to a system in which servo data is recorded on the same recording medium on which data to be read / written is recorded. Can also be applied to a method in which is recorded on a different recording medium.

[0056]

As described above, according to the present invention, in the deceleration control phase in the speed control, the system gain is switched according to the polarity of the error between the target speed and the moving speed (actual speed). Accordingly, it is possible to prevent the moving time of the head from increasing due to the variation in the characteristics of the control target, and as a result, the moving time can be improved and stabilized.

In addition, since the error between the target speed and the moving speed as a function of the elapsed moving time is fed back to the control output, the moving time of the head increases due to the variation in the characteristics of the control object, as described above. As a result, the travel time can be improved and stabilized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a speed control model according to a first embodiment of the present invention.

FIG. 2 is a diagram showing gain characteristics of a gain control unit in the speed control model shown in FIG.

FIG. 3 is a block diagram showing a configuration of a speed control device corresponding to the speed control model shown in FIG.

FIG. 4 is a flowchart for explaining the operation of the speed control device shown in FIG. 3;

FIG. 5 is a diagram showing a configuration of a speed control model according to a second embodiment of the present invention.

6 is a block diagram showing a configuration of a speed control device corresponding to the speed control model shown in FIG.

FIG. 7 is a flowchart for explaining the operation of the speed control device shown in FIG. 6;

FIG. 8 is a diagram illustrating a relationship between a moving time of a magnetic head and a target speed.

FIG. 9 is a diagram illustrating a relationship between a moving distance of a magnetic head and a target speed.

FIG. 10 is a diagram showing a relationship between a target speed and a moving speed by various controls.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Magnetic disk, 11 ... Magnetic head, 12 ... Amplifier, 13 ... Position detector, 14 ... A / D converter, 15 ... C
PU, 16: ROM, 16a and 16b: storage unit, 1
7 D / A converter, 18 Power amplifier, 19 VCM
(Voice coil motor), 20 ... carriage, 10a ...
Spindle motor, 21: Position detection unit, 22: Target speed generation unit, 23: Moving speed calculation unit, 24 and 28: Subtraction unit, 25: Compensation filter unit, 26: Gain control unit, 27
... Control object, 31 ... Position detection unit, 32 ... Moving speed calculation unit, 33, 37 and 38 ... Subtraction unit, 34 and 36 ...
Target speed generation unit, 35: time generation unit, 39, 40 and 42: gain control unit, 41: addition unit, 43: control target.

Claims (3)

(57) [Claims] 1. A recording medium on which servo data is recorded in advance, a head for recording / reproducing data on / from the recording medium, a head driving means for moving the head in a radial direction of the recording medium, and the head Position detecting means for generating position information indicating the current position of the head based on the servo data read from the CPU; and detecting the moving speed of the head based on the position information generated by the position detecting means. Moving speed detecting means; target speed detecting means for detecting a target speed corresponding to a distance from a current position of the head to a target track based on the position information generated by the position detecting means; Means for detecting an error speed between the target speed detected by the means and the moving speed detected by the moving speed detecting means. An error speed detecting means for switching the gain in accordance with the polarity of the error speed detected by the error speed detecting means, and driving the head driving means based on the switched gain and the error speed. A speed controller for a magnetic disk drive, comprising: a drive controller. 2. The head drive control means increases the gain when the moving speed is lower than the target speed, and decreases the gain when the moving speed is higher than the target speed. A speed controller for a magnetic disk drive according to claim 1. 3. A recording medium on which servo data is recorded in advance, a head for recording / reproducing data on / from the recording medium, a head driving means for moving the head in a radial direction of the recording medium, and the head Position detecting means for generating position information indicating the current position of the head based on the servo data read from the CPU; and detecting the moving speed of the head based on the position information generated by the position detecting means. Moving speed detecting means; and first target speed detecting means for detecting a first target speed corresponding to a distance from a current position of the head to a target track based on the position information generated by the position detecting means. And the first target speed detected by the first target speed detecting means and the shift detected by the moving speed detecting means. First error speed detecting means for detecting a first error speed with respect to the moving speed; and a second error speed corresponding to an elapsed time from the start of movement of the head, based on the position information generated by the position detecting means. A second target speed detecting means for detecting the target speed of the second target speed; and a second target speed between the second target speed detected by the second target speed detecting device and the moving speed detected by the moving speed detecting device. Second error speed detecting means for detecting the error speed of the first and second error speeds, and the first error speed detected by the first error speed detecting device and the second error speed detected by the second error speed detecting device. Error speed adding means for adding the error speed at a predetermined ratio; and head drive control means for driving the head driving means based on the error speed added by the error speed adding means. A speed controller for a magnetic disk drive, comprising: